Detailed explanations in West Bengal Board Class 10 Physical Science Book Solutions Chapter 6 Current Electricity offer valuable context and analysis.

WBBSE Class 10 Physical Science Chapter 6 Question Answer – Current Electricity

Very Short Answer Type Questions :

Question 1.
What is electric current?
Answer:
Electric current is general means a continuous flow of electrons, ions or any electrically charged particles through a medium.

Question 2.
What are conductors ?
Answer:
The substances through which electric charge flows easily are known as conductors.

Question 3.
What are non-conductors ?
Answer:
The substances which do not allow electric charge to pass through them are called non-conductors or insulators.

Question 4.
How can we define electric current in a quantitative way ?
Answer:
In a quantitative way we can say that the rate of flow of electric charge through any cross section of a conductor per unit time is called the electric current.

Question 5.
What do you mean by D.C. ?
Answer:
If the electric current always flow in the same direction then the current is called D.C. (Direct Current.)

Question 6.
What do you mean by A.C.?
Answer:
If the direction of current alternates i.e. changes periodically from one direction to opposite direction then the current is called A.C. (Alternating current).

Question 7.
What is electric cell?
Answer:
A device in which electrical energy is obtained from the chemical energy is known as electric cell.

Question 8.
What is negative electrode?
Answer:
The metal rod in which there is excess of negative charge is called negative electrode of cell.

Question 9.
What is positive electrode?
Answer:
The metal rod in which there is excess of positive charge is called positive electrode.

Question 10.
What is open circuit?
Answer:
When the electrodes of a cell are not connected by a conductor, externally, the cell is said to be in open circuit.

Question 11.
What is close circuit?
Answer:
When the electrodes are connected internally with a conductor, the cell is said to be in closed circuit.

Question 12.
What is emf of a cell?
Answer:
The potential difference between the electrodes of a cell in open circuit is called emf (electromotive force).

Question 13.
What is the direction of current in the external circuit of a cell?
Answer:
Current flows from positive electrode to negative electrode in the external circuit of a cell.

Question 14.
What is the emf of a simple voltaic cell?
Answer:
The emf of a simple voltaic cell is 1.08 volt.

Question 15.
What is the physical nature of electromotive force?
Answer:
Electromotive force is some energy.

Question 16.
What is the unit of charge in SI system?
Answer:
The unit of charge in the SI system is coulomb.

Question 17.
What is the SI unit of current strength?
Answer:
The SI unit of current strength is ampere.

Question 18.
What are the units of electromotive force and potential difference in SI system?
Answer:
The SI unit of both electromotive force and potential difference is volt.

Question 19.
What is the SI unit of resistance?
Answer:
The SI unit of resistance of Ohm.

Question 20.
State the cases in which Ohm’s law is not valid.
Answer:
Ohm’s law is not valid for current flowing through gases under low pressure, electrolytes and semi-conductors.

Question 21.
How does the resistance of a conductor depend on the cross section of the conductor?
Answer:
Resistance of the conductor decreases with increase of cross section.

Question 22.
In a system of resistors connected in parallel, how is the magnitude of the equivalent resistance related to the magnitude of the resistor of least value?
Answer:
Equivalent resistance is smaller than the resistance of smallest resistor.

Question 23.
How is the heat generated due to electric current through a resistor related to the strength of current?
Answer:
Heat is directly proportional to square of current.

Question 24.
How is the heat generated due to electric current in a resistor related to resistance of the resistor.
Answer:
Heat is directly proportional to resistance.

Question 25.
What is 1 B.O.T.?
Answer:
The total electric energy expended in 1 hour at the rate of 1 kilowatt is known as 1 B.O.T. (Board of Trade unit).

Question 26.
Which energy is converted to which other in an electric motor?
Answer:
In an electric motor, electric energy is converted to mechanical energy.

Question 27.
What is earthing?
Answer:
Earthing : It means to connect the metal case of an electrical appliance to the earth with the help of a metal wire.

Question 28.
What is the usual colour of a live wire?
Answer:
The usual colour of a live wire is red.

Question 29.
What is the usual colour of a neutral wire?
Answer:
The usual colour of a neutral wire is black.

Question 30.
What is the usual colour of the earthing wire?
Answer:
The usual colour of the neutral wire is green.

Question 31.
Which effect of electric current is demonstrated in an electromagnet?
Answer:
Magnetic effect.

Question 32.
How is current related to potential difference?
Answer:
Current is directly proportional to potential difference.

Question 33.
What is the unit of resistivity in CGS system?
Answer:
The unit of resistivity in CGS system is Ohm-Cm.

Question 34.
Current flows through a conductor from east to west, in which direction electrons flow through it?
Answer:
Electrons flow from west to east.

Question 35.
What is an electromagnet?
Answer:
An electromagnet is a temporary magnet produced by passing electtric current through an insulated copper wire coiled around a soft iron body.

Question 36.
What is the core of an electromagnet?
Answer:
The soft iron body around which an insulated copper wire is coiled is called the core of the electromagnet.

Question 37.
Mention two uses of electromagnet.
Answer:
Electromagnet is used in electric calling bell, electric motor.

Question 38.
What happens if the soft iron used in the electromagnet of an electric bell be replaced with steel?
Answer:
The bell will not work, since the steel body turns to a permanent magnet.

Question 39.
How does the strength of an electromagnet depend on the nubmer of turns of a solenoid?
Answer:
Number of turns of insulated wire per unit length of a solenoid increases strength of electromagnet.

Question 40.
What is the function of an electric switch?
Answer:
Electric switch is a very common and simple device used to stop or allow flow of electric current to an electric current to an electric appliance as and when needed.

Question 41.
What is voltmeier?
Answer:
A voltmeter is used to measure the potential difference between two points in a section of an electrical circuit.

Question 42.
What is an ammeter?
Answer:
An ammeter is used to measure the current flowing through an electric circuit.

Question 43.
What should be the resistance of an ideal ammeter?
Answer:
Ideally the resistance of ammeter should be zero.

Question 44.
What should be the reisstance of an ideal volmeter?
Answer:
Ideally the resistance of voltmeter should be infinity.

Question 45.
What are the metals used to prepare fuse wire?
Answer:
Usually fuses consist of fine wires made of an alloy of lead (75%) and a small amount of tin (25%).

Question 46.
What is the rating of a fuse wire?
Answer:
The maximum current that may be allowed to flow through fuse wire before it melts is called the rating of fuse wire.

Question 47.
What is the nature of electric charge on an ebonite rod, when it is rubbed with cut skin?
Answer:
Negative charge.

Question 48.
A glass rod is rubbed with silk. What type of charges do they acquire?
Answer:
Glass is positively charged and the silk is negatively charged.

Question 49.
What is the SI unit of electric charge ?
Answer:
Coulomb (C)

Question 50.
What is the least value of electric charge available?
Answer:
1.6 × 10^-19C

Question 51.
How many electrons will have a total charge of one coulomb?
Answer:
Number of electrons = \(\frac{q}{e}\) = \(\frac{1}{1.6 \times 10^{-19}}\) = 6.25 × 10¹⁸.

Question 52.
Name two basic properties of electric charge.
Answer:
(i) The electtric charge of an isolated system is conserved and (ii) the electric charge is quantised.

Question 53.
What is meant by conservation of charge?
Answer:
It means that the total electric charge in an isolated system remains constant.

Question 54.
How is the mass of a body affected on charging?
Answer:
The charging is due to transfer of electrons from one body to another. So, mass increases in the case of negatively charged body and decreases in the case of positively charged body.

Question 55.
In coulomb’s law, on what factors does the value of electrostatic force constant K depend?
Answer:
It depends upon the system of units used and on the interverning medium.

Question 56.
Electrostatic force between two charges is called central force. why?
Answer:
It acts along the line joining the centres of the charges, and hence, it is a central force.

Question 57.
Does a dipole experience a force, when placed in the non-uniform plectric field?
Answer:
Yes, it experiences a force.

Question 58.
What is electric flux ? Write its SI unit?
Answer:
The electric flux linked with a surface is the total number of lines passing through the surface. Its SI unit is Nm² C^-1.

Question 59.
What is electric potential?
Answer:
The electric potential at a point is the work done in bringing a unit positive charge from infinity to that point in the electric field.

Question 60.
What is electric potential energy?
Answer:
The electric potential energy is the work done in bringing charges from infinity to their respective positions to form the system.

Question 61.
Define electric potential difference between two points in an electric field.
Answer:
The electric potential difference between two points in an electric field is the work done in bringing a unit positive charge from one point to the other point.

Question 62.
Illustrate a condition in which electric field is zero but potential is not zero.
Answer:
Electric field inside a hollow charged sphere is zero but potential is not zero.

Question 63.
Illustrate a condition in which electric field is not zero but potential is zero.
Answer:
The electric field on the equatorial line of an electrical dipole is not zero but the potential is zero.

Question 64.
Define the unit of electric unit.
Answer:
The unit of current is ampere. It is the one coulomb of charge flowing through a conductor in one second.

Question 65.
What is the direction of conventional current?
Answer:
It is the direction opposite to the flow of electrons in a conductor under the influence of electric field.

Question 66.
What is current density?
Answer:
It is the current flowing per unit area of a conductor.

Question 67.
What is the direction of current density?
Answer:
Its direction is same as that of applied electric field.

Question 68.
What is meant by steady current?
Answer:
A current whose magnitude does not change with time.

Question 69.
What is meant by varying current?
Answer:
A current whose magnitude changes with time.

Question 70.
What is drift velocity?
Answer:
It is the average velocity with which a free-electron gets drifted in an conductor under the influence of an external electric field applied to the conductor.

Question 71.
How does the drift velocity of electrons in a metallic conductor vary with temperature?
Answer:
Drift velocity of a metal decreases with increase in temperature.

Question 72.
What do you mean by relaxation time or mean free time?
Answer:
It is average time interval between the two successive collisions between electron and ion in a conductor.

Question 73.
On what factors does the resistance of the conductor depend?
Answer:
The resistance varies with length of the conductor and inversely proportional to area of cross section of the conductor and increases with temperature of the conductor.

Question 74.
What is the difference between Ohmic and Non-Ohmic conductors?
Answer:
Ohmic conductors strictly obey Ohm’s law while Non-Ohmic conductors do not obey Ohm’s law.

Question 75.
What do you mean by conductivity of a material? Give its SI unit.
Answer:
It is the reciprocal of resistivity. Its SI unit is mho m^-1.

Question 76.
What is CFL ?
Answer:
CFL is compact fluorescent lamp.

Question 77.
What is LED ?
Answer:
LED is light emitting diode.

Question 78.
What is the value of EMF of a voltaic cell and that of a Leclanche cell ?
Answer:
The value of EMF of a voltaic cell is 1.08 volt and that of Leclanche cell is 1.5 volt.

Question 79.
What is the value of permitivity of vacuum?
Answer:
Its value is, ε₀ = 8.854 × 10^-12 C² N^-1 m^-2

Question 80.
What do you mean by EMF of a cell?
Answer:
EMF of a cell may be defined as the energy spent (or work done) per unit charge in taking one unit positive charge around the complete circuit.

Question 81.
What do you mean by internal resistance of a cell?
Answer:
The resistance offered by a cell to the flow of current when it passes through it, is called the internal resistance of that cell. It is generally represented by r.

Question 82.
Name of metal which behaves as a superconductor?
Answer:
Mercury below 4.2 K behaves as a superconductor.

Question 83.
Mention one use of superconductivity?
Answer:
Superconductons are used to construct very strong magnets.

Question 84.
Which effect of current is utilized in an electric bulb?
Answer:
The heating effect of current is utilized in an electric bulb.

Question 85.
Is Joule heating a reversible effect?
Answer:
The phenomenon of joule heating is an irreversible one-change of the direction of current does not reverse the heating effect.

Question 86.
Why are coils of electric toasters and irons made of an alloy rather than a pure metal ?
Answer:
The resistivity of an alloy is higher than the pure metal. Moreover, at higher temperature, the alloys do not melt readily. Hence, the coils of heating appliances such as electric toasters and irons are made of an alloy rather than a pure metal.

Question 87.
When an electric bulb is connected to a 12 V battery, it draws a current of 1A. What is the power of the bulb?
Answer:
Power of the bulb, P = 12 V × 1 A = 12 W

Question 88.
What is the full form of EER?
Answer:
The full form of EER is Energy Efficiency Ratio.

Question 89.
How can you define EER, say, for an air conditioner?
Answer:
Energy Efficiency Ratio (EER) for an air conditioner can be defined as follows: EER of AC = cooling capacity (in watt)/Power Consumption (in watt)

Question 90.
Show that, potential difference × electric current = electric power
Answer:
Electric power is the electric work done per unit time.
So, power P = Work done/time or, P = W/t
Putting W = V.Q = Vlt, we have, P = \(\frac{\mathrm{VIt}}{\mathrm{t}}\) = VI
∴ Electric Power (P) = Potential difference (V) × Electric current (I).

Question 91.
Which effect of current can be utilized in detecting a current carrying wire concealed in a wall?
Answer:
The electromagnetic effect can be utilized for the purpose.

Question 92.
Which rule is known as Motor rule?
Answer:
Fleming’s left hand rule is known as Motor rule.

Question 93.
Who first showed that a momentary electric current is set up in closed coll of wire by moving it near a magnet or in any other magnetic field?
Answer:
Michael Faraday (in 1831)

Question 94.
What type of energy transfer takes place in a dynamo?
Answer:
A dynamo converts mechanical energy into electrical energy and generates DC.

Question 95.
Mention a way to increase the magnitude of e.m.f generated in a generator.
Answer:
The magnitude of e.m.f. generated can be increased by increasing the strength of the magnetic field in the generator.

Question 96.
For a tube light, which circuit should be used?
Answer:
Since a tube light consumer less power, so it should be connected to the lighting circuit (5A).

Question 97.
For an air conditioner, which circuit should be used?
Answer:
Since an air conditioner consumes more power, so it must be connected to the 5 A power circuit.

Short answer type questions :

Question 1.
What do you mean by potential difference?
Answer:
Potential difference It is the electrical condition of a point in an electric field or on a current carrying conductor that indicates whether electrons will flow from it or it from another connected point.

Question 2.
What is the definition of coulomb ?
Answer:
Coulomb : It is the quantity of electric charge that passing through silver nitrate solution deposits 0.001118 g silver at the cathode.

Question 3.
What is the definition of ampere?
Answer:
Ampere : It is the current that flowing through silver nitrate solution for one second during electrolysis deposits 0.001118 g silver at the cathode.

Question 4.
What is the definition of ohm ?
Answer:
Ohm : If one ampere current flowing through a conductor establishes 1 volt potential difference between the two ends of the conductor, the resistance of the conductor is one ohm.

Question 5.
State Ohm’s law.
Answer:
Ohm’s law (1826) : The temperature and other physical conditions remaining constant the current flowing between any two points of a conductor is proportional to the potential difference between them.

Question 6.
Deduce the mathematical form of Ohm’s law.
Answer:
Mathematical form of Ohm’s law :
Let V_A and V_B are the potentials at the ends A and B of the conductor A B respectively.
So, the potential difference between the points is V_A – V_B=V (say).

Now, if current I flows through the conductor, then following ohm’s law, V α I
or, V = R I(R= constant, the resistance of conductor )
or, \(\frac{V}{I}\) = R

Question 7.
What is the definition of resistance from Ohm’s law ?
Answer:
Definition of resistance from Ohm’s law : The resistance of a conductor is a ratio of the potential difference between its ends to the current flowing through it.

Question 8.
On what factors does the resistance of a conductor depend ?
Answer:
Factors upon which the resistance of a conductor depends :
(i) Effect of length : Temperature, material and area of cross section remainning constant, the resistance (R) of a conductor is proportional to its length (1)
∴ R ∝ l (when temperature, material and cross-section are constant)
(ii) Effect of cross-section : Temperature, material and length remaining constant the resistance (R) of a conductor is inversely proportional to its area of cross-section (A)
∴ R ∝ \(\frac{1}{A}\) (When temperature, material and length are constant)

Question 9.
What is specific resistance ?
Answer:
Specific resistance : We know, R ∝ l when A is constant
R ∝ \(\frac{1}{A} \) when l is constant
When both length and the area of cross-section of a conductor vary, then from the law of joint variation, we can write,
R ∝ \(\frac{1}{A}\)
or, R = ρ \(\frac{1}{A}\) [ρ (rho) is the constant of proportionality and is known as the specific resistance of resistivity]
Now, if l = 1 and A = 1, then R = ρ

Definition: The specific resistance or resistivity of a material is numerically equal to the resistance of a conductor of the material of length 1 metre and area of cross-section 1 m².

Question 10.
Specific resistance of copper 20°C is 1.6 × 10^-6 ohm-cm, what do you mean by it ?
Answer:
Specific resistance of copper 20°C is 1.6 × 10^-6 ohm-cm}, it means: Resistance across the opposite faces of a copper cube of 1 cm side, at 20° C is 1.6 × 10^-6 ohm.

Question 11.
What do you mean by combination of resistance ?
Answer:
Combination of resistance : In different electrical circuit more than are resistance are connected together. This is known as combination of resistances. Usually two types of combination are used-
(i) Series combination
(ii) Parallel combination

Question 12.
Define equivalent resistance.
Answer:
Equivalent resistance : The single resistance, instead of multiple resistance in a circuit, keeps the voltage and current unchanged, is called equivalent resistance of those resistances.

Question 13.
What do you mean by series combination?
Answer:
Series combination: In this combination resistances are so connected that extreme end of one resistance is joined to the begining end of next resistance and so on. In this connection same current flows through all the resistances. If three resistors r₁ r₂ r₃ connected in series, the same current I passes through each then their equivalent resistance R will be.

Question 14.
What do you mean by parallel combination?
Answer:
Parallel combination : A number of resistors are said to be connected in parallel when they are placed side by side and their corresponding ends joined together so that the main current is distributed among them.

If the individual resistances is parallel combination are r₁ r₂ r₃ then their equivalent resistance R is given by
\(\frac{1}{R}=\frac{1}{r_1}+\frac{1}{r_2}+\frac{1}{r_3}\)
So, to create a low resistance out of few relatively high resistances, those needed to be connected to parallel combination. Equivalent resistance in parallel combination is lesser than the lowest of the individual resistances.

Question 15.
What is internal resistance of a cell ?
Answer:
Internal resistance: The small resistance offered by the electrolyte of a cell to the electric charges flowing through it from the negative to the positive plate is known as the internal resistance of the cell.

Question 16.
What is watt-hours ? Whose unit is it ?
Answer:
Watt-hour : If an elecrtrical machine of power one watt operates for one hour then one watt hour amount of energy is said to be spent.
1 watt-hour = 1 watt × 1 hour
= 1 watt × 3600 sec = 3600 J
Unit of electrical energy is watt-hour.

Question 17.
Define 1 kilowatt-hour ?
Answer:
If a machine of 1 kilo-hour operates for one hour the amount of energy spent is known as kilo-watt hour. This amount of energy is also known as Board of Trade Unit (B. O. T, units).

Question 18.
Why is nichrome wire used in electrically heated appliances ?
Answer:
(i) Explanation : Nichrome, an alloy of iron (24%), nickel (60%) and chromium (16%) was much larger resistance than copper and it is about 80 times. Thus, large quantity of heat produces when electricity flows through it. It neither melts nor gets oxidized even when it is red hot. For these reasons nichrome wire is used in most of electrically heated appliances.

Question 19.
What is short circuiting and what is overloading.
Answer:
Short circuiting : It means direct connection between the two terminals of a source of electricity or through a metallic wire of feeble resistance. As a result, large current flows through the connecting wire which melts due to overheating and therefore further flow of current stops.
Overloading : It is another dangerous effect which is caused by drawing excessive current when a number of high-powered electrical appliances are simultaneously switched on.

Question 20.
What is a fuse ? What is fuse rating ?
Answer:
Fuse : For the safety of the electrical gadgets one thin wire made of an alloy of lead (75 %) and tin (25%) and which has high resistance and low melting is kept in a insulator box of china clay. The thin coil is called fuse wire.
The wire is kept in series with the main circuit of the household electrical appliances.
If for some reason or other there is a surge of the current the household electical appliances may get burn. Under such condition the fuse wire melts and there by cut of the entire circuit and saves the domestic electrical equipments. Rating of fuse wire: The maximum current that may be allowed to flow through a fuse wire before it melts is called the rating of fuse wire.

Question 21.
What is earthing? How is a person saved from electric shock even if the live wire accidentally touches the metal body of an electric iron the person working with.
Answer:
Earthing : It means to connect a body or the metal case of an electrical appliance to the earth with the help of a metal wire, called, earth wire.
This wire protects a person using the appliance from electric shocks.
If the live wire by chance touches the metal part of an electrical appliance which has been earthed, the current passes directly to the earth through the earth wire.

Question 22.
What is Oersted’s experiment ?
Answer:
Oersted’s experiment : In this experiment, a conductor is held above and parallel to a freely rotatable pivoted magnetic needle. It is found that the magnetic needle deflects due to current flow in the conductor. The deflection increases with increase of current and it reverses when current is reversed.

Question 23.
State Ampere’s swimming rule.
Answer:
Ampere’s swimming rule : If a man be imagined to be swimming along a current carrying wire in the direction of the current (south to north) with his face turned towards a freely rotating magnetic needle, then the north pole of the needle will be deflected towards his left hand.

Question 24.
State Fleming’s left hand rule.
Answer:
Fleming’s left hand rule: If the thumb, the first finger and the middle finger of the left hand be held mutually perpendicular to each other in such a way that the first finger points in the direction of the magnetic field and the second finger to that of the current, then the thumb will indicate the direction at motion of the conductor.

Question 25.
Show how is Fleming’s left hand rule verified by Barlow’s wheel.
Answer:
Explanation : Barlow’s wheel is an arrangement to demonstrate action of magnet on current that verifies Fleming’s left hand rule.

According to the diagram, the current carrying conductor, the toothed wheel is situated in between the magnetic poles. So, when current is allowed to flow, the wheel rotates following Fleming’s left hand rule. On reversing the current the wheel rotates in oppsoite direction following the same rule.

Question 26.
On what factors does the relocing of rotation of Barlow’s wheel depend?
Answer:
Factors responsible for the speed of rotation :

1. Rotational speed increases with current and vice versa.
2. Rotational speed increases with intensity of magnetic field and vice versa.
3. If alternating current is used instead of Direct current, the wheel will try to reverse its direction with the change in direction of current resulting no rotation.

Question 27.
How can the direction of rotation of Barlow’s wheel be changed?
Answer:
Factors governing the direction of rotation of Barlow’s wheel :

1. The direction of rotation will reverse if direction of current is reversed keeping direction of magnetic field unchanged.
2. The direction of rotation will reverse if direction of magnetic field is reversed keeping direction of current unchanged.
3. The direction of rotation will remain unchanged in both direction of magnetic field and direction of current are reversed.

Question 28.
A bulb is marked ‘230 V-60 W’ what does it indicate?
Answer:
Explanation: When the bulb is used in an electrical line of potential difference 230 volts, 60 joules electrical Work per second is performed due to flow of electric current through the filament of the bulb.

Question 29.
What do you mean by the statement. ‘Potential difference between two points in an electric field is 5 volts’?
Answer:
Explanation: ‘Potential difference between two points in an electric field is 5 volts’- this statement means an external agent has to do 5 joules work to carry 1 coulomb positive charge from a point at lower potential to a point at higher potential in the electric field.

Question 30.
Why resistivity is also called specific resistance ?
Answer:
Explanation : Resistivity is also called specific resistance as resistivity of a material is the resistance offered by the material of specified dimensions unit length unit cross sectional area.

Question 31.
What is electric motor ?
Answer:
Electric Motor: The device or machine which converts the electrical energy into mechanical energy is known as Electric Motor.
An insulated copper coil, wound over a suitable frame rotates in a magnetic field when electric current passes through the coil.

Question 32.
How can the strength of the motor be increased ?
Answer:
The strength of an electric motor can be increased by :

1. increasing the current in the armature.
2. increasing the strength of magnetic field.
3. increasing the number of turns in the armature.

Question 33.
What is solenoid ?
Answer:

Solenoid: If many turns an insulated wire wound around a cylinder the resulting coil is known as solenoid. The soft iron body around which an insulated copper wire is coiled is known as the core of the electromagnet.

Question 34.
What is electromagnet ?
Answer:
Electromagnet: If soft iron is kept in a current carrying solenoid, then that soft iron behaves like a magnet so long as the current passes. This magnet is known as electromagnet.

Question 35.
How can the strength of electromagnet be increased ?
Answer:
The strength of electromagnet be increased by :

1. increasing the number of turns of solenoid.
2. increasing the current through the solenoid.
3. changing the core of the electromagnet.
4. if the core is ‘U’ shaped, then the distance between the poles is minimum.

Question 36.
State a few applications of eleciromagnet in daily life.
Answer:
Uses of electromagnets :

1. They are widely used in cranes for lifting and removing heavy beams etc. made of iron or steel in factories.
2. Physicians use special types of electromagent to remove small pieces of iron from the eye of a patient.
3. They are used in loudspeakers, receivers of telephone etc.

Question 37.
What is voltmeter ?
Answer:
Voltmeter : A voltmeter is used to measure the potential difference between two points in a section of an electrical circuit ; the voltmeter is connected parallel to the section.

Question 38.
What is ammeter ?
Answer:
Ammeter : It is used to measure the current flowing through an electric circuit where the ammeter is connected in series.

Question 39.
Why is e.m.f. (electromotive forces) of an electric cell is greater than p.d. (potential difference) ?
Answer:
Explanation : The difference of potential between two poles of a cell in open circuit is e.m.f. of the cell, the potential difference between the poles in closed circuit is p.d. (potential difference) of the cell. Now, in a closed circuit, a part of the e.m.f. is expended to overcome the internal resistance of the ce: is offered by the electrolyte of the cell. So, p.d. is less than the e.m.t. cell or e.m.f. is greater than p.d.

Broad Answer Type Questions

Question 1.
What is the difference between e.m.f. and p.d. ?
Answer:
Difference between e.m.f and p.d. :

e.m.f (Electromotive Foce)	p.d (Potential Difference)
i. It causes conversion of some other form of energy into electrical energy.	i. It causes conservation of electrical energy into some other form of energy.
ii. It is the potential difference across two terminals of an open circuit cell.	ii. It is the potential difference between two terminals of a closed circuit cell.
iii. The magnitude of e.m.f. is greater than p.d. in a cell.	iii. The magnitude of p.d. is lesser than e.m.f. in a cell.
iv. It is considered as the cause of p.d.	iv. Potential difference is the result/effect of e.m.f.
v. It does not depend on the resistance of the circuit.	v. Potential difference across any two points of a circuit depends on the resistance of that portion of the circuit.

Question 2.
State Joule’s laws of heating effect of current.
Answer:
Joule’s Laws (1841) :
(i) First law : The amount of heat produced in a conductor in a given interval of time is proportional to the square of the current passed. Thus if H be the amount of heat generated in a conductor having resistance R when current I passes through it in time t, then
H ∝ P² (when R and t are kept constant).

(ii) Second Law : The amount of heat produced by a given current in a given time is proportional of the resistance of the conductor.
H ∝ R (When I and t are kept constant)

(iii) Third Law : The amount of heat produced in a given conductor by a given current is proportional to the time for which the current passes.
H ∝ t (When I and R are kept constant)
Combining the three laws, we have
H ∝ I² R T (when I, R and t vary)
or, H = \(\frac{I^2 R T}{\mathrm{~J}}\)
(J = mechanical equivalent of heat = 4.2 joule/calorie)
If I be in ampere, R in ohm, t in second and H in calorie, then
H = \(\frac{I^2 R T}{4 \cdot 2}\)
∴ H = 0.24 F ² RT calorie

Question 3.
What is the difference between electromagnet and a natural or permanent magnet ?
Answer:
Difference between electromagnet and natural magnet :

Electromagnet	Natural magnet
i. The magnetism of this type of magnet almost disappears as soon as the current is stopped i.e. it is a temporary one.	i. If properly maintained magnetism of this type of magnet is almost permanent.
ii. It can be made very strong.	ii. It is usually not very strong.
iii. Strength of the magnet by changing the strength of the current.	iii. Strength of the magnet cannot be changed.
iv. By changing the number of turns per unit length of the coil, the strength of the magnet can be changed.	iv. Strength of the magnet cannot be changed.
v. By changing the direction of current polarity of the magnet can be easily reversed.	v. In this case polarity of the magnet cannot be reversed easily.

Question 4.
An electric heater works both in A.C. and D. C. lines but Barlow’s wheel works only in D. C.- Why ?
Answer:
Explanation Generation of heat in a resistor due to a current depends on magnitude of the current not on its direction. Moreover, the produced heat H ∝ I², so even if the oppositely directed current of A.C. be taken with negative direction, on being squared, it becomes positive. So, a heater can work both in A.C. and D.C.
the rotation of Barlow’s wheel in a given magnetic field depends upon the direction of current. The direction of rotation will reverse if direction of current is reversed keeping direction of magnetic field infact.
Now, in A.C., the direction of current reverses alternately and so frequently that, as soon as Barlow’s wheel is set to rotate in one direction, the reverse current flows into it tending to rotate it oppositely. This happens continuously and very frequently, so the wheel remains static.

Numerical Problems :

Example 1:
The resistance of a conductor is 100 hm; a current of 5 ampere is flowing through it. What will be the p.d. at the two ends of the conductor?
Answer:
R = 10 ohm
I = 5 ampere
V = p.d. = ?
We know,
V = RI
or, V = 10 × 5 = 50 volts

Example 2:
A current of 2A flows through a conductor. The p.d. across the conductor is 50 volts. What is the resistance?
Answer:
We know,
V = R I
or, R = \(\frac{V}{I}\) = \(\frac{50}{2}\)
I = 2 volts
R = 25 ohm

Example 3:
10 ampere current is allowed to a conductor for 1 minute. Find the amount of charge flown.
Answer:
I = 10 ampere
t = 1 minute = 60 sec
Q = ?
We know,
Q = I × t
or, Q = 10 × 60 = 600
∴ Q = 600 coulomb

Example 4:
Potential difference across two points of a conductor is 60 volts. Resistance of the conductor is 10 ohm. Find the’current through the conductor.
Answer:
V = 60 volts
R = 10 ohm
I = ?
We know,
V = R I
or, I = \(\frac{V}{R}\) = \(\frac{60}{10}\) = 6
or, I = 6 ampere

Example 5:
A current of 2 ampere is passed through a conductor of resistance 4 \mathrm{ohm}. Find the potential difference across the conductor.
Answer:
I = 2 unit
R = 2 unit
V = ?
We know,
V = I × R
or, V = 2 × 4 = 8
∴ V = 8 volts

Example 6:
Resistance of one conductor is double that of the other. What will be the ratio of current through these two conductor if they are subjected to same potential difference.
Answer:
Let the resistance of the conductors are R and 2 R. Let both of them are subjected to same potential difference of V. So, naturally currents in the conductors will be as follows :

Example 7:
2 units of current is flowing through a conauctor or of 2 units. What is the potential difference at the ends of the conductor?
Answer:
I = 2 ampere
R = 4 ohm
V = ?
We know,
V = R . I
or, V = 2 × 2 = 4 unit

Example 8:
The resistance per metre of a wire is 1.2 ohm and its specific resistance is 60.28 × 10^-8 ohm-m. Find the radius of the wire.
Answer:
R = 1.2 ohm
I = 1 meter
ρ = 60.28 × 10^-18ohm-m
A = ?
We know,
R = ρ \(\frac{1}{A}\) or, A= \(\frac{\rho l}{R}\)
or, A = \(\frac{60 \cdot 28 \times 10^{-8} \times 1}{1 \cdot 2}\)
∴ A 50.2 × 10^-8 m²
Again, if r be the radius of the wire,
πr² = A = 50.2 × 10^-8 or, r²=\(\frac{50 \cdot 2 \times 10^{-8}}{3 \cdot 14}\) 16× 10^-8 m²
∴ r = 4 × 10^-14 m = 0.04 cm

Example 9:
There are two copper wires of equal length. The radius of one is twice the other. Find the ratio of their resistances.
Answer:
r = radius of the wire
We know,

∴ The thinner wire has a resistance four times the resistance of the thicker wire.

Example 10:
The resistivity of a substance is 9 \times 10^-8 \mathrm{ohm} . \mathrm{m}. What length of the wire of that material, having diameter 0.3 cm} will give a resistance of 100 \mathrm{ohm} ?
Answer:
We know,

Example 11:
The resistance of wire of cross-section area 0.01 cm² is 10 ohm. What is the length of the wire? The specific resistance of the wire is 50 × 10^-6 ohm-cm.
Answer:
We know,
R = 10 ohm
A = 0.01 cm²
ρ = 50 × 10^-6 ohm-cm
l = ?
R = ρ \(\frac{1}{A}\) or, l = \(\frac{RA}{\rho}\)
or, l = \(\frac{10 \times 0.01}{50 \times 10^{-6}}\)
∴ l = 2000 cm

Example 12 :
The length and area of cross-section of a wire are double of these of another wire of same material. Find the ratio of their resistances.
Answer:
Let the length of wires be 2 l and l and their areas of cross. Section be 2 A and A respectively. If \rho be the resistivity of the material of the wires, then their resistance R₁ and R₂ will be given by
R₁= \(\frac{\rho 2 l}{2 A}\) and R₂ = \(\frac{\rho l}{A}\)
∴ \(\frac{R_1}{R_2}\) = \(\frac{1}{1}\) or, R₁ : R₂ = 1 : 1

Example 13 :
Find the specific resistance of the material of a wire of length 100 cm, area of cross-section 0.2 cm2 and resistance 2 ohm.
Answer:
R = 2 ohm
l = 100 cm
A = 0.2 cm²
ρ = ?
R = ρ × \(\frac{1}{A}\)
∴ ρ = \(\frac{R A}{l}\) = \(\frac{2 \times 0.2}{100}\) =40 ×s 10^-4 ohm-cm

Example 14 :
Three resistors 1 ohm, 2 ohm and 3 ohm are connected in parallel. What will be their equivalent resistance?
Answer:
We know, for parallel combination,

Example 15 :
Three wires of resistance 2 ohm, 3 ohm and 5 ohm are connected in series with a cell of e.m.f. 5 volt. What will be the current through each wire?
Answer:
We know, for series combination the equivalent resistance
R = r₁ + r₂ + r₃ = 2 + 3 + 5 = 10 ohm
We also know,
I = \(\frac{V}{R}\) = \(\frac{5}{10}\) = 0.5 A

Example 16 :
Find effective resistance of the resistors 2 ohm, 4 ohm, 5 ohm connected in (i) series and (ii) parallel.
Answer:
We know, for series combination equivalent resistance
R = r₁ + r₂ + r₃ = 2 + 4 + 5 = 11 ohm
We also know, for parallel combination equivalent resistance

Example 17 :
In a circuit 2 ohm and 3 ohm resistors are connected in series to the parallel arrangement of 2 ohm and 3 ohm resistors. Calculate the resistance of the circuit.
Answer:
Let R be the equivalent reistance of 2 ohm and 3 ohm arranged in parallel.
So, \(\frac{1}{R}\) = \(\frac{1}{2}\) + \(\frac{1}{3}\) = \(\frac{5}{6}\)
∴ \(\frac{1}{R}\) = \(\frac{5}{6}\) or, R = \(\frac{6}{5}\) = 1.2 ohm
Now, 2 ohm and 3 ohm resistors are connected in series with 1.2 ohm. So, the resistance of the circuit = (2 + 3 + 1.2) ohm = 6.2 ohm.

Example 18 :
A current of 0.5 ampere passes through a wire of resistance 2.5 ohm for 1 hour. Find the heat produced.
Answer:
I = 0.5 ampere
R = 2.5 ohm
t = 1 hr = 3600 sec
H = ?
We know, H = \(\frac{I^2 R T}{J}=\frac{I^2 R T}{4 \cdot 2}\)
∴ H=\(\frac{(0.5)^2 \times 2.5 \times 3600}{4.2}\) = 535.7 calorie

Example 19 :
Two electric bulbs marked 220V-60W are used daily for 5 hours for 10 days. If the price of each unit of electrical energy be 65 paise. What will be the cost for it ?
Answer:
From the problem we get, Total power of the two bulbs = 2 × 60 watt =120 watt
Electrical energy consumed per day = 120 watt × 5 hour = 600 watt-hour
∴ Total energy consumed in 10 days = 600 × 10 = 6000 watt hour
= \(\frac{6000}{1000}\) = 6 kilo watt-hour = 6 B.O.T. unit
∴ cost of electrical energy at 65 paise per unit = 6 × 65 paise = Rs. 3.90

Example 20 :
The same current passes for the same time through two wires the resistance of one is double that of the other. What is the ratio of quantities of heat developed in the two wries?
Answer:
Let the resistances of the wires be 2 R and R and the quantities of heat produced in them be H₁ and H₂respectively. Then from Joule’s second law we get,
\(\frac{H_1}{H_2}=\frac{2 R}{R}=\frac{2}{1}\) or, H₁: H₂ = 2: 1

Detailed explanations in West Bengal Board Class 10 Physical Science Book Solutions Chapter 8.4 Inorganic Chemistry in the Laboratory and in Industry offer valuable context and analysis.

WBBSE Class 10 Physical Science Chapter 8.4 Question Answer – Inorganic Chemistry in the Laboratory and in Industry

A. Ammonia

Very Short Answer Type Questions

Question 1.
Name the chemicals required for the preparation of ammonia in laboratory
Answer:
Chemicals required :

• Ammonium chloride (NH₄Cl)
• Quick lime (CaO) or dry slaked lime [Ca(OH)₂]

Question 2.
What is the characteristic smell of ammonia ?
Answer:
Characteristic smell of ammonia Pungent

Question 3.
What is the nature of aqueous solution of ammonia ?
Answer:
Nature of aqueous solution of ammonia : alkaline

Question 4.
State one method for identification of ammonia.
Answer:
Ammonia has a typical pungent smell.

Question 5.
Which particular substance is used to dry ammonia gas ?
Answer:
Ammonia is dried with calcium oxide (CaO).

Question 6.
What colour is obtained when ammonia burns in presence of oxygen?
Answer:
Ammonia burns in presence of oxygen with a greenish yellow flame forming nitrogen and water.
4NH₃ + 3O₂ = 2N₂ + 6H₂O

Question 7.
What is Nessler’s reagent ?
Answer:
Nessler’s reagent Nessler’s reagent is an alkaline solution (KOH) of po­tassium mercuric iodide [K₂Hgl₄]

Question 8.
What happens when red litmus paper is placed in aqueous solution of ammonia ?
Answer:
The aqueous solution of ammonia is basic in nature so it turns red litmus to blue.

Question 9.
State one use of ammonium sulphate.
Answer:
Use of ammonium sulphate : as fertilizer.

Question 10.
What is the amount of ammonia present in liquor ammonia ?
Answer:
35% (by weight)

Question 11.
Is ammonia heavier or lighter than air ?
Answer:
Ammonia is lighter than air.
[Vapour density of air = 144 ; vapour density of ammonia = 8-5 ]

Question 12.
State one use of liquid ammonia.
Answer:
Use of liquid ammonia : as a refrigerant in ice making.

Question 13.
Give an example of formation of solid by the combination of two gases.
Answer:
Ammonia gas reacts with hydrogen chloride gas forming solid ammonium chloride.
NH₃(gas) + HCl (gas) = NH₄Cl (solid)

Question 14.
How is ammonia collected in laboratory ?
Answer:
Collection of ammonia Ammonia is lighter than air, it may be collected by the downward displacement of air.

Question 15.
What colour is obtained when ammonia reacts with Nessler’s reagent?
Answer:
Ammonia produces brown colouration in Nessler’s reagent.

Question 16.
Which compound of nitrogen has fractional oxidation number ?
Answer:
Hydrazoic acid (HN₃)
Nitrogen has \(\left(-\frac{1}{3}\right)\) oxidation number in hydrazoic acid.

Question 17.
Which hydride of nitrogen has no oxidising property ?
Answer:
Ammonia has no oxidising property.

Question 18.
Which gas is obtained when a mixture of ammonium sulphate and sodium hydroxide is heated ?
Answer:
Ammonia (NH₃) gas.

Question 19.
How ammonium sulphate is obtained without using sulphuric acid ?
Answer:
CaSO₄ + 2NH₃ + CO₂ + H₂O = CaCO₃ + (NH₄)₂SO₄

Question 20.
Two gaseous compounds of nitrogen react with each other to form nitrogen. What are the two gaseous compounds of nitrogen ?
Answer:

Short answer type questions

Question 1.
Why is conc. H₂SO₄ not used for drying ammonia gas ?
Answer:
Ammonia is a basic compound. So it forms salt with cone. H₂SO₄.
For this reason cone. H₂SO₄ is not used for drying ammonia gas.
2NH₃ + H₂SO₄ = (NH₄)₂SO₄

Question 2.
Why is anhydrous CaCl₂ not used for drying ammonia gas ?
Answer
Ammonia forms an additive compound with anhydrous CaCl₂.
CaCl₂ + 8NH₃ = CaCl₂, 8NH₃ (additive compound)

Question 3.
Why is P₂O_s not used for drying ammonia gas ?
Answer:
Ammonia is a basic compound. P₂O_s is an acidic oxide. So it forms salt with P₂O₅ SO P₂O₅ is not used for drying ammonia gas.
6NH₃ + P₂O_s + 3H₂O = 2(NH₄)₃PO₄

Question 4.
Why CaO is used for drying agent of ammonia ?
Answer:
CaO is used for drying agent of ammonia : Ammonia is a basic com­pound. It is dried of using a basic drying agent i.e. Quick lime (CaO) which has no action on ammonia.

Question 5.
What is liquor ammonia ?
Answer:
Liquor ammonia A saturated (35% by weight) aqueous solution of am­monia (sp. gr. = 088) is called liquor ammonia.

Question 6.
Prove that ammonia has reducing property.
Answer:
Reducing property of ammonia : When ammonia is passed over strongly heated black cupric oxide which is reduced to red metallic copper and am­monia is oxidised to nitrogen.

Question 7.
State about solubility of ammonia in water.
Answer
Solubility of ammonia is water : Ammonia is highly soluble in water. One volume of water can dissolve about 1299 volumes ammonia at N.T.P A concentrated aqueous solution of ammonia is called ammonia.

Question 8.
What are the differences between liquid ammonia and liquor ammonia ?
Answer
Difference between liquid ammonia and liquor ammonia :
There is a sharp difference between liquid ammonia and liquor ammonia. The first one is the liquified ammonia gas which has formula NH₃, while the second one is the concentrated solution of ammonia which has formula NH₄OH.

Question 9.
How will you prove that ammonia contains nitrogen ?
Answer
Ammonia contains nitrogen : Ammonia gas when passed over heated cupric oxide produces colourless gas having no smell.
3CuO + 2NH₃ = 3Cu + 3H₂O + N₂
When the colourless gas is passed over heated magnesium, magnesium nitride (Mg₃N₂), the white powder produces.
3Mg + N₂ = Mg₃N₂
When the white powder is boiled with water it will produce pungent smell gas NH₃
Mg₃N₂+ 6H₂O = 3Mg(OH)₂ + 2NH₃↑
This reaction proves that the colourless gas is nitrogen. This reaction also proves that one of the constituents of ammonia is nitrogen.

Question 10.
What precautions should be taken to combat the effect of ammonia leaked from industries and ammonia tanks ?
Answer
Precautions for ammonia If accidentally, ammonia gas leaks from indus­tries and ammonia tanks, heavy shower of water should be applied in the atmosphere that is filled with the leaked gas. If at any time, tanks filled with ammonia gas are required to be shifted somewhere, the carrier of tanks must also carry plenty of water that may be used to spray in the air filled with accidental leakage of ammonia gas.

Question 11.
How does ammonia react with sodium ?
Answer
Reaction of ammonia with sodium Heated sodium metal at 400°C reacts with ammonia producing sodamide and hydrogen gas.
2NH₃ + 2Na = 2NaNH₂ + H₂↑
This reaction proves that ammonia contains hydrogen.

Question 12.
How does ammonia react with chlorine ?
Answer
Reaction of ammonia with chlorine : Ammonia reacts with chlorine in two ways.
(i) When ammonia is excess : Excess ammonia is oxidised by chlorine forming nitrogen and is reduced to hydrochloric acid. Hydrochloric acid thus formed combines with ammonia producing ammonium chloride.

(ii) When chlorine is excess : When excess chlorine reacts ammonia forming nascent nitrogen which again combines with chlorine producing nitrogen trichloride, an oily yellow explosive compound.
NH₃ + 3Cl₂ = 3HCl + NCl₃

Question 13.
Show with an equation what happens when ammonia is burnt in oxygen.
Answer:
Ammonia is burnt in oxygen Ammonia is neither combustible nor a supporter of combustion. But ammonia burns in presence of oxygen with a greenish yellow flame forming nitrogen and water.
4NH₃ + 3O₂ = 2N₂↑ + 6H₂O

Question 14.
How does aqueous ammonia react with aluminium chloride and ferric chloride solutions ?
Answer:
(i) Reaction of aqueous ammonia with aluminium chloride solution: Aqueous solution of ammonia (NH₄OH) reacts with aluminium chloride forming white gelatinus precipitate of aluminium hydroxide.
AlCl₃ + 3NH₄OH = Al(OH)₃↓(white) + 3NH₄Cl

(ii) Reaction of aqueous ammonia with ferric chloride solution :
Aqueous solution of ammonia (NH₄OH) reacts with ferric chloride solution forming brown precipitate of ferric hydroxide.
FeCl₃ + 3NH₄OH = Fe(OH)₃↓(brown) + 3NH₄Cl

Question 15.
State with reasons two precautions taken during preparation of ammonia in laboratory.
Answer:
Precautions taken during preparation of ammonia in laboratory :

• The components ammonium chloride (NH₄Cl) and calcium hydroxide [Ca(OH)₂] should be dry to avoid evolution of ammonia while mixing the two.
• The mixture of the components should fill about half the flask to leave enough space for easy passage of the evolved gas.

Question 16.
State some uses of ammonia.
Answer:
Uses of ammonia :

• It is used for the industrial preparation of nitric acid and sodium carbonate.
• Large quantities of ammonia are used in the manufacture of fertilizers, such as urea, ammonium phosphate etc.
• Ammonia is used as solvent.
• Liquid ammonia is used as a refrigerant in ice making.
• Ammonia is used as laboratory reagent.
• It is also used in pharmaceutical industries and also in the preparation of smelling salt.

Question 17.
Give an example of formation of a solid by combination of two gases.
Answer:
Formation of a solid by combination of two gases : Ammonia gas reacts with hydrogen chloride gas forming a solid ammonium chloride. This is an example of formation of a solid by the combination of two gases.
NH₃ (gas) + HCl (gas) = NH₄Cl (solid)

Question 18.
State how does ammonia react with HCl, H₂SO₄, HNO, acids.
Answer:
Reaction of ammonia with acids : Ammonia is a base, it readily reacts with an acid to form salt.
NH₃ + HCl = NH₄Cl
2NH₃ + H₂SO₄ = (NH₄)₂SO₄
NH₃ + HNO₃ = NH₄NO₃
Aqueous solution of ammonia reacts with acids to form salt and water.
NH₄OH + HCl = NH₄Cl(salt) + H₂O₃
2NH₄OH + H₂SO₄ = (NH₄)₂SO₄(salt) + 2H₂O
NH₄OH + HNO₃ = NH₄NO₃(salt) + H₂O

Question 19.
How is urea obtained from ammonia?
Ans. Preparation of urea from ammonia: Ammonia reacts with carbon dioxide at 200°C and 150 atm pressure to form urea.
CO₂ + 2NH₃ = CO(NH₂)₂ (urea) + H₂O

Question 20.
How does aqueous ammonia react with copper sulphate solution?
Answer:
Reaction of aqueous ammonia with copper sulphate solution When aqueous ammonia i.e. ammonium hydroxide is slowly added to a copper sul­phate solution, a pale blue precipitate of basic copper sulphate is first formed. On adding excess of ammonium hydroxide, the precipitate dissolves forming a deep solution of the complex compound called copper tetramine sulphate.
2CuSO₄+ 2NH₄OH = CuSO₄. Cu(OH)₂ + (NH₄)₂SO₄
CuSO₄ .Cu(OH)₂ + 6NH₄OH + (NH₄)₂SO₄ = 2[Cu(NH₃)SO₄+ 8H₂O

Broad Answer Type Questions

Question 1.
How ammonia is prepared in laboratory ?
Answer:
Laboratory preparation of Ammonia :
(a) Chemicals required : Ammonium chloride (NH₄Cl) and quick lime (CaO) or dry slaked lime [Ca(OH)₂

(b) Condition Normally ammonia gas is obtained in the laboratory by heating a mixture of ammonium chloride with slaked lime. Instead of using slaked lime quick lime may also be used. NH₄>Cl, Ca(OH)₂ or CaO should be in powdered form and dry. The round bottomed flask should be half filled with the mixture of the two for easy escape of ammonia gas formed.

(c) Collection Ammonia is lighter than air, it may be collected by the downward displacement of air. Ammonia is not collected through the downward displacement of water because, it is highly soluble in water.

(d) Equations of the reaction :
2NH₄Cl + Ca(OH)₂ = 2NH₃↑+ CaCl₂ + 2H₂O
2NH₄Cl + CaO = 2NH₃↑ + CaCl₂ + H₂O

(e) Precautions : The ingradients, the test-tube, the delivery pipes and the gas-jar should be absolutely dry. All the connections in the apparatus should be leak-proof.

(f) Drying of ammonia : As ammonia is a basic substance, it cannot be dried by acidic drying agents like cone. H₂SO₄ or P₂O_s. The gas is absorbed by fused CaCl₂ with the formation of an addition compound CaCl₂.8NH₃. So, fused CaCl₂ cannot be used to dry ammonia. It is best dried with the basic drying agent, quick lime (CaO).

Question 2.
Prove by experiment that ammonia is dissolved in water and produces alkaline solution.
Answer:
Fountain experiment :
Arrangement of the experiment : A flask is filled with dry ammonia gas and its mouth is corked. The flask is kept in inverted position and is damped to a stand. Through a hole in the cork one end of a glass tube is introduced inside the flask. This end of the tube inside the flask is shaped into a jet. The other end of the tube dips in some red litmus solution taken in a beaker.

Operation : Now ice or ether is poured upon the flask.

Observation : A blue fountain produces inside the flask.

Explination Due to evaporation of ether the flask is cooled. Ammonia gas inside the flask contracts, as a result there is a partial vacuum inside the flask. At this stage if stop cock is opened the red litmus solution rushes inside the flask and ammonia is dissolved in it. Due to vaccum created inside there is a formation of fountain and the solution becomes blue.

Conclusion : This experiment proves that ammonia is highly soluble in water and the aqueous solution is alkaline.

Question 3.
How is ammonia identified ?
Answer:
Identification of ammonia :
(a) Ammonia is easily detected by its pungent smell.

(b) A glass rod dipped in into hydrochloric acid is then held into ammonia a white fumes is observed due to formation of ammonium chloride.
NH₃ + HCl = NH₄Cl (white fumes)

(c) Ammonia turns moist red litmus paper into blue.

(d) Ammonia produces brown colouration or precipitate in Nessler’s reagent.

(e) A strip of filter paper, soaked in mercurous nitrate solution, when exposed to ammonia gas, turns black.

B. Sulphuretted Hydrogen (H₂S)

Very Short answer type questions 

Question 1.
Which acid is used to prepare H₂S gas in laboratory ?
Answer:
Dilute sulphuric acid.

Question 2.
During preparation of H₂S gas in laboratory, how Is the gas collected?
Answer:
By upward displacement of air.

Question 3.
What happens when H₂S gas is passed through acidified yellow ferric chloride solution ?
Answer:
Yellow ferric chloride solution reduces to colourless ferrous chloride solution.

Question 4.
How is H₂S gas dried In laboratory preparation ?
Answer:
By passing the gas through phosphorus pentoxide (P₂O₅).

Question 5.
How does H₇S gas smell ?
Answer:
It has a smell of rotten egg.

Question 6.
How does H₂S gas react with blue litmus ?
Answer:
It turns blue litmus red.

Question 7.
What gas is used in detecting metallic radical in laboratory ?
Answer:
Sulphuretted hydrogen (H₂S)

Question 8.
Is H₂S gas heavier or lighter than air ?
Answer:
H₂S gas is heavier than air.

Question 9.
Is H₇S combustible or a supporter of combustion ?
Answer:
H₂S is a combustible gas.

Question 10.
Why is an old silver made substance turned to black ?
Answer:
Due to formation of silver sulphide (Ag₂S).

Question 11.
What is the common use of hydrogen sulphide in laboratory ?
Answer:
For the identification of basic radical (metal ion).

Question 12.
Name the chemicals required for preparation of H₂S in laboratory.
Answer:
Chemicals required for preparation of H₂S :

• Ferrous sulphide (FeS)
• Dilute sulphuric acid (H₂SO₄)

Question 13.
Is HCl acid suitable for preparation of H₂S ?
Answer:
No. As HCl is very volatile.

Question 14.
Mention one identifying test for H₂S.
Answer:
Lead acetate paper turns black when it is held in H₂S gas.

Question 15.
What is the density of H₂S at NTP ?
Answer:
Density of H₂S gas is 1-53 g/L at NTP

Question 16.
Give the name of a gas which is soluble in cold water but insoluble in hot water.
Answer:
Hydrogen sulphide (H₂S)

Question 17.
Which gas is used to identify basic radical ?
Answer:
Hydrogen sulphide (H₂S)

Question 18.
What happens when H₂S gas is passed through a blue coloured solution of CuSO₂ ?
Answer:
Black precipitate of CuS is formed.

Question 19.
Is H₂S acidic or basic gas ?
Answer:
H₂S is acidic gas.

Question 20.
How many types of salts are formed by H₂S ?
Answer:
Since H₂S is a bibasic acid, it gives two types of salt, one is acid salt and other is normal salt.

Question 21.
Give the name of a poisonous gas.
Answer:
Hydrogen sulphide (H₂S).

Short Answer Type Questions

Question 1.
Name the chemicals required for preparation of H₂S in laboratory. Write down the equation of reaction.
Answer:
Chemicals required for preparation of H₂S in laboratory :
Ferrous sulphide (FeS) and dilute sulphuric acid (H₂SO₄)
Equation : FeS + H₂SO₄ = FeSO₄ + H₂S↑

Question 2.
Is HCl acid suitable for preparation of H₂S ? Give reason.
Answer:
HCl acid is not suitable for preparation of H₂S.
Cause : HCl acid is not chosen due to volatile nature of HCl. During the preparation, HCl vapour that may be formed will accompany the evolved H₂S and will make it impure.

Question 3.
Is HNO₃ acid suitable for preparation of H₂S? Give reason.
Answer:
HNO₃ acid is not suitable for preparation of H₂S.
Nitric acid cannot be used in the preparation, because it is an oxidising agent and H₂S is a reducing agent. Nitric acid will oxidise H₂S to sulphur and will thus hamper the reaction.

Question 4.
Mention one identifying test for H₂S.
Answer:
Identification of H₂S: Hydrogen sulphide is passed through a solution of sodium hydroxide solution and then sodium nitroprusside solution is added to it. The solution turns violet.

Question 5.
How does H₂S react with cone. HNO_a?
Answer:
Reaction of H₂S with cone HNO₃ :
H₂S-reduces cone. HNO₃ to brown nitrogen dioxide (NO₂) and is itself oxidised to sulphur.
Equation : H₂S + 2HNO₃ = 2NO₂↑ + S↓+ 2H₂O

Question 6.
How does H₂S react with cone. H₂SQ₄ ?
Answer:
Reaction of H S with cone. H₂SO₄ : H₂S) reduces cone. H₂SO₄ to SO₂ and is itself oxidised to sulphur.
Equation : H₂S + H₂SO₄ = SO₂↑ + S↓ + 2H₂O

Question 7.
Write down the reaction of H₂S with NaOH.
Answer:
Reaction of H₂S with NaOH : H₂S reacting with NaOH produces acid salt in the first step and normal salt in the second step along with water in both the steps.

Question 8.
Which substance is used for drying H₂S and why ?
Answer:
Drying of H₂S gas : The most suitable drying agent for H₂S is the acidic oxide P₂O₅, that does not react with H₂S which is also of acidic nature.

Question 9.
What is the density of H₂S and state about its solubility in water at ordinary temperature and in hot water.
Answer:
Density of H₂S : Density of the gas is T53 g/L at NTR
Solubility of H₂S in water : It is moderately soluble in water at ordinary temperature but insoluble in hot water.

Question 10.
What happens when H₂S is burnt in small and excess supply of oxygen ?
Answer:
H₂S is burnt in small supply of oxygen : During burning of H₂S if the supply of oxygen is low, the gas burns with a blue flame and deposits sulphur. 2H₂S + O₂ = 2S↓ + 2H₂O
H₂S is burnt in excess supply of oxygen : In an excessive supply of oxygen the gas burns with a blue flame and produces sulphur dioxide and water.

Question 11.
Show that H₂S is a reducing agent.
Answer:
Reducing property of H₂S : Hydrogen sulphide is a very good reducing agent. H₂S reduces acidified yellow solution of ferric chloride to colourless ferrous chloride.

Question 12.
What happens when H₂S is passed through acidified solution of FeCl_a?
Answer:
Yellow ferric chloride solution is reduced by H₂S giving rise colourless ferrous chloride and H₂S itself on oxidation gives a precipitate of sulphur.
Equation : 2FeCl₃ + H₂S = 2FeCl₂ + 2HCl + S₄

Question 13.
What happens when H₂S is passed through acidified solution of CuSO₄?
Answer:
If H₂S is passed through acidified blue coloured solution of CuSO₄ then black precipitate of cupric sulphide (CuS) is formed.
Example:

Question 14.
What happens when H₂S is passed through acidified solution of Pb(NO₃)₂
Answer:
If H₂S is passed through acidified colourless solution of Pb(NO₃)₂ then black precipitate of lead sulphide (PbS) is formed.
Example:

Question 15.
What happens when H₂S comes in contact with a paper soaked in lead acetate ?
Answer:
A paper soaked in lead acetate [Pb(CH₃COO)₂] turns black with H₂S gas due to formation of black lead sulphide (PbS).
Equation:

Question 16.
Mention the uses of hydrogen sulphide.
Answer:
Uses of hydrogen sulphide :

• H₂S is used as a reagent in the separation of metal ions in group analysis.
• H₂S is sometimes used as a reducing agent.

Broad answer type questions

Question 1.
Describe laboratory method of preparation of H₂S with the points:
(i) chemicals required
(ii) condition
(iii) equation of reaction
(iv) drying agent
(v) collection
Answer:
(i) Chemicals required Ferrous sulphide (FeS) and dilute sulphuric acid (H₂SO₄)
(ii) Condition Hydrogen sulphide is prepared in the laboratory by the action of dil. H₂SO₄ on pieces of ferrous sulphide (FeS) at ordinary temperature.
(iii) Equation of reaction : FeS + H₂SO₄ = FeSO₄ + H₂S↑
(iv) Drying agent The gas is passed through P₂O₅ to dry it.
(v) Collection : Because the gas is heavier than air it is collected over the upward displacement of air.

Question 2.
What precautions should be taken during preparation and handling of H₂S ?
Answer:
Precautions taken during preparation of H₂S : Hydrogen sulphide is a poisonous gas and is harmful at concentrations above 0-1% by volume in air. So, due precautions should be taken not to inhale the gas not to allow its prolonged contact with skin during handling.

During preparation of the gas caution must be taken so that excessive gas does not spread in the atmosphere of laboratory. To do this, sulphuric acid should be added in the wolfe’s bottle in small quantities and in steps.

C. Nitrogen

Very short answer type questions

Question 1.
Name the chemicals used In laboratory method of preparation of nitrogen.
Answer:
Chemicals required : Ammonium chloride (NH₄Cl) and sodium nitrite (NaNO₂).

Question 2.
State what you know about solubility of nitrogen in water.
Answer:
Solubility of nitrogen in water is about 23-5 ml/L at NTR It is almost half that of oxygen.

Question 3.
What is the density of nitrogen?
Answer:
Density of nitrogen 125 g/L at NTR

Question 4.
How is nitrogen prepared in laboratory dried?
Answer:
Nitrogen has is dried by passing the gas through concentrated sulphuric acid (H₂SO₄).

Question 5.
What is the percentage of nitrogen in air by volume?
Answer:
Percentage of nitrogen in air by volume : 77 17%

Question 6.
What would happen if there were no nitrogen in the atmosphere?
Answer:
In absence of nitrogen burning in atmosphere would be vigorous and uncontrollable.

Question 7.
What is the use of liquid nitrogen?
Answer:
Liquid nitrogen (b.p.-195’8°C) is used to produce low temperature in scientific research.

Question 8.
Is nitrogen heavier or lighter than air?
Answer:
Nitrogen is slightly lighter than air.

Question 9.
Give a name of nitrogen containing inorganic fertilizer.
Answer:
Nitrogen containing inorganic fertilizer : Ammonium nitrate (NH₄NO₃).

Question 10.
Which gas is used in gas-thermometer?
Answer:
Nitrogen gas is used in gas-thermometer.

Question 11.
Which gas is used in electric bulb?
Answer:
Nitrogen gas is used in electric bulb.

Question 12.
What is nitrogen trihydride?
Answer:
Nitrogen trihydride is ammonia

Question 13.
Which gas is presentjarge amount in atmosphere?
Answer:
Nitrogen gas is present large amount in atmosphere.

Question 14.
What is nitrolim?
Answer:
Nitrolim : Mixture of calcium cyanamide and carbon is known as nitrolim.

Question 15.
Which gas is used to create inert atmosphere during^hemical reactions.
Answer:
Nitrogen gas is used to create inert atmosphere during chemical reactions.

Question 16.
What are the two essential gaseous components of the atmospheric air ?
Answer:
Two essential gaseous components are :
(i) Oxygen
(ii) Nitrogen

Question 17.
Which plants absorb nitrogen directly from air ?
Answer:
A few leguminous plants such as pea, bean, clover etc. can absorb nitrogen directly from air.

Question 18.
What are the ways of fixation of nitrogen?
Answer:
There are two ways of fixation of nitrogen:
By electric discharge
Bio-chemical reaction through bacteria.

Short Answer Type Questions

Question 1.
How does nitrogen react with oxygen?
Answer:
Reaction of nitrogen with oxygen : Nitrogen reacts with oxygen forming nitric oxide under the influence of electric arc at a temperature of 3000°C.
\(\mathrm{N}_2+\mathrm{O}_2 \rightleftharpoons 2 \mathrm{NO} \text { – heat (Endothermic reaction) }\)

Question 2.
Why Is the solution of ammonium chloride and sodium nitrite is heated to produce nitrogen instead of heating ammonium nitrite directly?
Answer:
Nitrogen gas is not prepared by heating ammonium nitrite (NH4NO2) directly, for in that case rapid explosive dissociation of ammonium nitrite takes place.

Question 3.
How does nitrogen react with magnesium ?
Answer:
Reaction with magnesium : When turnings of magnesium metal are strongly heated in nitrogen gas, the metal directly combines with nitrogen to form magnesium nitride
(Mg₃N₂).
3Mg + N₂ = Mg₃N₂

Question 4.
What happens if magnesium nitride is boiled with water ?
Answer:
Magnesium nitride is boiled with water to form magnesium hydroxide and ammonia.
Mg₃N₂ + 6H₂O = 3Mg(OH)₂ + 2NH₃ 

Question 5.
What is nitrolim? How it is formed? Mention its important use.
Answer:
Nitrolim: When small lumps of white calcium carbide (CaC₂) are heated in nitrogen gas at about 1100°C, calcium cyanamide (CaNCN) is formed, along with the separation of carbon particles (black). The blackish brown mixture of the products (CaNCN + C) is commercially known as nitrolim. Use of nitrolim : It is largely used as a fertilizer.

Question 6.
State the uses of nitrogen.
Answer:
Uses of nitrogen :

• It is used in the industrial preparation of ammonia and nitric acid.
• It is used for the production of fertilizer, such as ammonium sulphate, am­monium nitrate.
• Liquid nitrogen (b.p. -195’8°C) is used as condenser.
• In many chemical reactions, nitrogen is used as inert medium.
• It is used in the preparation of electric bulb and gas thermometer.

Question 7.
Why gaseous nitrogen is chemically quite inactive at ordinary temperatures, but it is active at higher temperatures ?
Answer:
Chemical nature of gaseous nitrogen : The unreactivity of nitrogen at ordinary temperatures, is due to the structure of nitrogen molecule (N₂), in which two nitrogen atoms are bonded together by three covalent bonds (N ≡ N). The force of attraction of two nitrogen atoms so bonded is very high. So large amount of energy (generally heat energy) is required to break up this bond to set free the two nitrogen atoms so that they can enter into chemical combination.

Question 8.
State the physical properties of nitrogen.
Answer:
Physical properties of nitrogen :

• It is colourless gas without smell or taste,
• Density of the gas is 1.25 g/L at NTR
• It is slightly soluble in water.
  Solubility of nitrogen in water is about 23-5 ml/L at NTR

Broad Answer Type Questions 

Question 1.
Describe the laboratory method of preparation of nitrogen. State the following matters :
(a) chemicals required
(b) condition
(c) drying
(d) chemical equation
(e) collection of gas.
Answer:
Laboratory method of preparation of nitrogen :
(a) Chemicals required :

• Sodium nitrite (NaNO₂)
• Ammonium chloride (NH₄Cl)

(b) Condition : The chemicals ammonium chloride and sodium nitrite must not be in solid state but as solution. The mixture is heated gently to evolve nitrogen gas.

(c) drying : The nitrogen gas is dried by passing through a U-tube containing cone., sulphuric acid.

Chemical equation:

(e) Collection of gas : Though nitrogen gas is slightly soluble in water, it is collected by the downward displacement of water.

Question 2.
State briefly the significance of the presence of nitrogen in air.
Answer:
Significance of the presence of nitrogen in air : Nitrogen in air dilutes oxygen present therein. Oxygen is a very active oxidant. The mixture of nitrogen with oxygen in air moderates the intense activity of pure oxygen in the processes of respiration, combustion etc, which would have otherwise occurred very rapidly.

The intake of only oxygen during respiration would have caused increased rate of respiration, causing excessive burning of body tissues. This would have caused high and unchecked rise in the temperature of body, which results death. Without nitrogen in air, the combustion of earthly materials would have been explosively vigorous.

The huge amount (about 78% by volume) of nitrogen in air can be ab­sorbed by certain symbiotic bacteria, such as Rhizobium leguminouserum, R. japonicum etc. Nitrogen is converted to nitrogenous salts in nature by many chemical and biochemical process. Proteins, the complex nitrogenous compounds, which are absolutely essential for living beings are also indirectly formed from the nitrogen of air.

Question 3.
State the two possible ways of reaction of nitrogen with hydrogen, also write down the connected equations of reaction.
Answer:
First type Nitrogen combines with hydrogen under the influence of electric spark producing ammonia gas.

Second type : Nitrogen also combines with hydrogen at 550°C under 200 atmospheric pressure in presence of iron catalyst to form nitrogen gas.

Question 4.
State two important ways of fixation of nitrogen.
Answer:
Two ways of fixation of nitrogen :
By electric discharge : During electric discharge in the atmosphere nitrogen and oxygen present in air combine to produce nitric oxide. The produced nitric oxide is then oxidised by atmospheric oxygen to form nitrogen dioxide. Later this oxide upon missing with water vapour or rain water product nitric acid which falls upon our earth.

Nitric acid is then reacted with the bases present in the soil forming nitrate salts.

iii. Fixation of nitrogen due to bacteria Some micro organism and blue green algae convert nitrogen present in air to ammoiate salt by bio-chemical process. When the animal and plant bodies undergo decay most of the nitrogen (proteins) is liberated as ammonia which is oxidised in the soil by the combined action of nitrosifying and nitrifying becteria into nitrate to be again assimilated by plants. A portion of the fixed nitrogen is set free by the action of denitrifying bacteria of the soil.

(d) Hydrogen Chloride (Hydrochloric acid),
Nitric acid and Sulphuric acid

Very Short Answer Type Questions )

Question 1.
Why is concentrated sulphuric acid used to prepare HCl in laboratory ?
Answer:
Concentrated sulphuric acid is used to prepare HCl in laboratory because concentrated sulphuric acid is less volatile.

Question 2.
What is muriatic acid ?
Answer:
Muriatic acid is the commercial name of hydrochloric acid (HCl).

Question 3.
Why is not nitric acid used to prepare HCl ?
Answer:
Nitric acid is not used to prepare HCl as nitric acid is highly volatile and a strong oxidant.

Question 4.
State about solubility of HCl gas in water ?
Answer:
HCl gas is highly soluble in water.

Question 5.
Why is not hydrochloric acid used to prepare nitric acid ?
Answer:
Hydrochloric acid is not used to prepare nitric acid as hydrochloric acid is more volatile than nitric acid.

Question 6.
What is fuming nitric acid ?
Answer:
Fuming nitric acid is a product produced by dissolving excess nitrogen di­oxide in nitric acid.

Question 7.
What is acid rain ?
Answer:
Dissolved NO₂and SO₂ of atmosphere produce acids which come down along with rain. This is called acid rain.

Question 8.
What is oleum ?
Answer:
Oleum is sulphuric acid in which excess sulphur trioxide is dissolved.

Question 9.
What is stone cancer ?
Answer:
Corrosion of marble or stone due to acid rain is called stone cancer.

Question 10.
What is the commercial name of nitric acid ?
Answer:
The commercial name of nitric acid is aqua fortis.

Question 11.
How does copper react with sulphuric acid ?
Answer:
Copper reacts with hot and concentrated sulphuric acid.

Question 12.
Why does sugar of white colour turns to a black mass in contact with concentrated sulphuric acid ?
Answer:
Concentrated sulphuric acid absorbs the water molecules present in sugar molecules leaving behind black carbon.

Question 13.
What is passive iron ?
Answer:
Chemically inactive iron is called passive iron.

Question 14.
What is the commercial name of sulphuric acid ?
Answer:
The commercial name of sulphuric acid is oil of vitriol.

Question 15.
Which acid produces hydrogen reacting with metals Mg and Mn only?
Answer:
Dilute and cold nitric acid (HNO₃) produces hydrogen reacting with Mg and Mn.

Question 16.
Name an acid which has great affinity to water.
Answer:
Concentrated sulphuric acid (H₂SO₄) has great affinity to water.

Question 17.
Which acid is identified by ring test ?
Answer:
Nitric acid is identified by ring test.

Question 18.
Which acid turns blue copper sulphate to white anhydrous salt ?
Answer:
Concentrated sulphuric acid (H₂SO₄) turns blue copper sulphate to white anhydrous salt.

Question 19.
Among HCl, H₂SO₄ and HNO₃ acid which acid has the lowest boiling point ?
Answer:
HCl acid has the lowest boiling point.

Question 20.
What is aqua regia ?
Answer:
Aqua regia is a mixture of 3 volumes concentrated hydrochloric acid and 1 volume concentrated nitric acid.

Question 21.
Which acid is detected by AgNO₃ solution ?
Answer:
Hydrochloric acid is detected by AgNO₃ solution.

Question 22.
What is royal water ?
Answer:
Aqua regia is also known as royal water.

Question 23.
What is fuming sulphuric acid ?
Answer:
Fuming sulphuric acid or oleum is obtained when sulphur trioxide is passed over 98% sulphuric acid.

Question 24.
How is hydrogen chloride gas collected in laboratory ?
Answer:
Hydrogen chloride gas is heavier than air so it is collected by upward dis­placement of air.

Question 25.
Name one air pollutant gas.
Answer:
Air polutant gas is nitrogen dioxide (NO₂)

Question 26.
Which gas pollutes air form Goldsmith’s workshop ?
Answer:
Nitrogen dioxide (NO₂)

Question 27.
Which mineral acid has no reducing property ?
Answer:
Nitric acid (HNO₃)

Question 28.
What is the commercial name of nitric acid ?
Answer:
The commercial name of nitric acid is aquafortis.

Question 29.
State one use of aqua regia.
Answer:
Noble metals like gold, platinum are soluble in aqua regia.

Question 30.
State one use of sulphuric acid.
Answer:
Sulphuric acid is used to prepare fertilizer like ammonium sulphate [NH₂SO₄]

Question 31.
State one use of nitric acid.
Answer:
Nitric acid is used for the manufacture of high explosive like nitroglycerine.

Question 32.
Name a reducing acid.
Answer:
Hydrochloric acid (HCl) is an example of reducing acid.

Question 33.
What is the catalyst used during preparation of nitric acid by the Ostwald process ?
Answer:
Platinum gauze catalyst is used during preparation of nitric acid by the Ostwald process.

Question 34.
Which catalyst is used during preparation of sulphuric acid by contact process ?
Answer:
Platinum asbestos or vanadium pentoxide catalyst is used during preparation of sulphuric acid by contact process.

Question 35.
Which acid is detected by BaCl, solution ?
Answer:
Sulphuric acid (H₂SO₄) is detected by BaCl solution.

Question 36.
What is the basicity of sulphuric acid ?
Answer:
The basicity of sulphuric acid is 2.

Question 37.
Which acid is used as a cleaning agent in bathroom ?
Answer:
Muriatic acid (HCl) is used as a cleaning agent in bathroom.

Question 38.
Among HCl, H₂SO₄ and HNO which acid has the highest point?
Answer:
Sulphuric acid has the highest boiling point [338°C] among HCl, H₂SO₄ and HNO₃

Question 39.
Which acid is called ‘king of chemicals’ ?
Answer:
Sulphuric acid (H₂SO₄) is called ‘king of chemicals’.

Question 40.
Which acid is gas at ordinary temperature ?
Answer:
Hydrochloric acid.

Question 41.
Dense white fumes are formed when a glass-rod, moistened with strong ammonia solution, is held in a gas. Identify the gas.
Answer:
The gas is ammonia.

Question 42.
What is laughing gas ?
Answer:
Nitrous oxide (N₂O) is called laughing gas.

Question 43.
Can dry hydrogen chloride gas turn blue litmus paperred ?
Answer:
No. Dry hydrogen chloride gas turns a moist blue litmus paper red.

Question 44.
What is the molecular weight of nitric acid ?
Answer:
The molecular weight of nitric acid is 63.

Question 45.
What is the specific gravity of sulphuric acid ?
Answer:
The specific gravity of sulphuric acid is 1.84.

Question 46.
Name one metal ion that can be identified by using H₂S.
Answer:
Cu²⁺

Question 47.
What is commercial name of pyrosulphuric acid?
Answer:
Oleum (H₂S₂O₇)

Question 48.
What is the catalyst used for preparation of HNO₃ by ‘ostwald process’
Answer:
Platinum wie gauze is used as the catalyst for the purpose.

Question 49.
What is liquor ammonia?
Answer:
Liquor ammonia is a saturated solution of ammonia in water.

Question 50.
What is Nessler’s reagent?
Answer:
Alkaline solution of potassium tetra iodo mercurate, K₂[Hgl₄] is known as Nessler’s neagent.

Question 51.
What is aqua fortis?
Answer:
Nitric acid (HNO₃) was known to the alchemists as aqua fortis.

Question 52.
Why do old oil paintings turn black on exposure to H₂S?
Answer:
The paints used in oil paintings contain lead that react with weak dibasic H₂S to form black lead sulphide (PbS).

Question 53.
Name a gas which can be prepared in kipp’s apparatus.
Answer:
H₂S can be readily and intermittently prepared in kipp’s apparatus.

Question 54.
What happens when calcium cyanamide is heated with super heated steam?
Answer:
When calcium cyanamide is heated with super heated steam (especially in an autoclave), it is hydrolysed to form ammonia.

Question 55.
What happens when ammonia is burnt in air?
Answer:
When ammonia is burnt in air, it burns with a greenish-yellow flame forming nitrogen and steam.

Question 56.
H₂SO₄ is industrially produced by which process?
Answer:
H₂SO₄ is industrially produced by contact process.

Question 57.
Why H₂S gas is collected by upward displacement of air?
Answer:
H₂S is soluble in cold water and is heavier than air. So it is not collected over water and is collected by upward displacement of air.

Short Answer Type Questions

Question 1.
Describe the preparation of hydrogen chloride in laboratory with mention of
(i) chemical equation
(ii) collection
Answer:
Preparation of hydrogen chloride in laboratory : Chemical equation:
(i) If the mixture of sodium chloride and concentrated sulphuric acid is heated at 150°C – 200°C then sodium bisulphate and hydrogen chloride gas are produced.

(ii) If it is heated at 500°C then sodium sulphate and hydrogen chloride gas are evolved.

Collection : Since dry hydrogen chloride gas is heavier than air it is col­lected by upward displacement of air.

Question 2.
Why the reaction is kept at lower temperature during the preparation of hydrogen chloride in laboratory from sodium chloride and cone, sulphuric acid ?
Answer:
Reason In the laboratory the reaction is kept at lower temperature because:

• at high temperature the flask used in the preparation may be cracked.
• Sodium sulphate at higher temperature forms a hard crust and sticks to the glass. Its removal is then difficult.

Question 3.
Why hydrogen chloride is not collected over displacement of water?
Answer:
Reason : Hydrogen chloride is highly soluble in water. It has been found that at 0°C, 450 ml of hydrogen chloride is dissolved in 1 ml of water. So, it is not collected over displacement of water.

Question 4.
What is the compound necessary for drying of hydrogen chloride gas?
Answer:
Drying of hydrogen chloride : To remove water vapour, hydrogen chloride gas is passed over cone. H₂SO₄.

Hydrogen chloride is acidic nature. Hence, it cannot be dried over quick lime (CaO), caustic soda (NaOH) or caustic potash (KOH).

Question 5.
How is hydrochloric acid prepared ?
Answer:
Preparation of hydrochloric acid : Hydrochloric acid is a solution of hydrogen chloride gas in water. Cone, hydrochloric acid, as used in the laboratory is not 100% pure hydrochloric acid. It is about 38% solution of hydrogen chloride gas in water.

Hydrogen chloride gas is passed into a beaker containing cold water till the water is saturated with the gas. The contents of the beaker is a concentrated solution of hydrochloric acid.

Question 6.
Hydrochloric acid is not prepared by dissolving hydrogen chloride gas in water directly—why ?
Answer:
Reason As hydrogen chloride gas is highly soluble in water and the rate of dissolving of HCl gas in water is much higher than the rate of formation of HCl gas as a result there is a vacuum in the flask. To fill up the vacu­um water in the beaker enters into the flask and creates explosion when it contacts with sulphuric acid present in the flask.

Question 7.
Nitric acid is not used in the preparation of hydrochloric acid—why?
Answer:
Explanation :
(a) Nitric acid is not used because during the preparation of hydrogen chloride gas, nitric acid oxidises the evolved hydrogen chloride gas into chlorine gas.
Reaction HNO₃ + _;3HCl = NOCl + 2[Cl] + 2H₂O

(b) Hydrochloric acid (b. p. 86°C) and hydrogen chloride are volatile in nature. So they will be collected jointly in a receiver where nitric acid may oxidise hydrogen chloride into chlorine. On the other hand H₂SO₄(b.p. 338°C) is non-volatile; so, this is not happened.

Question 8.
State two physical properties of HC:
Answer:
Physical properties of HCl:

• It is a colourless gas with a choking smell and strongly fuming in moist air, hydrogen chloride is 127 times as heavy as air ; it neither burns nor supports burning.
• It is highly soluble in water. At 0°C, 450 ml of hydrogen chloride gas is dissolved in 1 ml of water.

Question 9.
How is pure hydrogen chloride prepared ?
Answer:
Preparation of pure hydrogen chloride Pure hydrogen chloride is obtained by the action of water upon silicon tetrachloride. Equation : SiCl₄ + 4H₂O = Si(OH)₄ + 4HCl

Question 10.
State the reaction of HCl with Na.
Answer:
Hydrogen chloride neither burns in air nor supports combustion. However burning sodium continues to burn in the gas with a bright yellow flame producing hydrogen and anhydrous sodium chloride.
Equation : 2Na + 2HCl = 2NaCl + H₂↑

Question 11.
Show the acidic property of hydrochloric acid.
Answer:
The aqueous solution of hydrochloric acid is a strong acid :

dissolves base metals, liberating hydrogen and forming metallic chlorides,
e.g. Zn + 2HCl = ZnCl₂ + H₂↑
The order of activity of the metals for liberating hydrogen may be stated as:
Ca > Mg > Al > Zn > Fe > Sn.

Question 12.
How copper and silver react with hydrochloric acid ?
Answer:
Generally, copper, silver are not attacked by hydrochloric acid. In presence of air, copper and silver react with very slowly producing corresponding chlorides and water.
Equations :

• 2Cu + 4HCl + O₂ = 2CuCl2₂ + 2H₂O
• 4Ag + 4HCl + O₂ = 4AgCl + 2H₂O

Question 13.
How does ammonia react with hydrogen chloride
Answer:
Reaction of ammonia with hydrogen chloride : Ammonia in contact with hydrogen chloride gives dense white fumes of solid ammonium chlo­ride. This reaction is an example of the formation of a solid product by the interaction of two gases.
Equation : NH₃(g) + HCl(g) = NH₄Cl(s)

Question 14.
What is reaction between Na₂CO₃ and HCl ?
Answer:
Reaction of Na₂CO₃ with HCl :
HCl reacts with Na₂CO_s to literate carbon dioxide.
Na₂CO₃ + 2HCl = 2NaCl + CO₂↑ + H₂O

Question 15.
State the action of hydrochloric acid with oxidising agent like MnO₂ and KMnO₄.
Answer:
Reaction of hydrochloric acid with MnO₂and KMnO₄
Manganese dioxide (MnO₂ oxidises hot and concentrated hydrochloric acid to greenwish yellow chloride.Potassium permanganate oxidises the hydrochloric acid at the ordinary tem­perature.

Question 16.
Show the presence of chloride ion in hydrochloric acid.
Answer:
Presence of chloride ion in hydrochloric acid : When hydrochloric acid is added to a solution of silver nitrate, a white precipitate of the chloride of silver is obtained. Silver chloride is insoluble in nitric acid but soluble in ammonium hydroxide.
Equation : AgNO₃ + HCl = AgCl↓ + HNO₃ 

Question 17.
How is hydrochloric acid identified?
Answer:
Identification of hydrochloric acid : When silver nitrate solution is added to hydrochloric acid taken in a test tube, curdy white precipitate of silver chloride is formed. The precipitate is insoluble in nitric acid but dissolves in ammonium hydroxide forming a clear solution of complex salt argento ammonium chloride. Equations :

• AgNO₃ + HCl = AgCl↓ + HNO₃
• AgCl + 2NH₄OH = [Ag(NH₃)₂]Cl + 2H₂O

Question 18.
State the identification of hydrogen chloride gas.
Answer:
Identification of hydrogen chloride gas : Dense white fumes are formed when a glass-rod, moistened with strong ammonia solution, is held in the hydrogen chloride gas.
Equation : NH₃(g) + HCl (g) = NH₄Cl (s)

Question 19.
What are the uses of hydrochloric acid ?
Answer:
Uses of hydrochloric acid :

• It is used in dyeing and calico-printing,
• It is used as a cleaning agent in galvaning and tinplating,
• It is used to prepare aqua-regia,
• It is used in the manufacture of glucose, glue and many useful metal-chlorides.

Question 20.
Describe the preparation of nitric acid in laboratory with mention of
(i) chemical required
(ii) chemical reaction.
Answer:
Preparation of nitric acid in laboratory :
Chemical required :

• Chille salt petre (NaNO₃) or nitre (KNO₃)
• Cone. Sulphuric acid.

Reaction occurs in two steps :

(a) If the reaction is kept at 200°C-300°C then sodium bisulphate and nitric acid are produced.

(b) At 800°C, sodium sulphate and nitric acid are formed in the reaction between sodium nitrate and concentrated sulphuric acid.
2NaNO₂+ H₂SO₄ = Na₂SO₄ + 2HNO₄

Question 21.
Why nitric acid is prepared at lower temperature (200°C) in laboratory?
Answer:
Nitric acid is prepared at lower temperature (200°C) in laboratory because :

• At high temperature nitric acid decomposes.
  4HNO₃ = 4NO₂ + O₂ + 2H₂O
• Nitric acid vapour attacks glass surface of the retort.
• Sodium sulphate (Na₂SO₄) formed at the higher temperature sticks to glass and is difficult to remove from the glass retort.

Question 22.
Why is cone, sulphuric acid used instead of cone, hydrochloric acid in the preparation of nitric acid in laboratory ?
Answer:
Choice of acid : In the preparation of an acid, the reacting acid must be less volatile than the acid to be prepared.Hence, cone. H₂SO₄(b.p. 338°C) is chosen because it is less volatile than nitric acid (b.p. 86°C). Hydrochloric acid is more volatile than nitric acid, so hydrochloric acid is not used. Beside this hydrochloric acid reacts with produced nitric acid to form nitrosyl chloride, chlorine and water.
3HCl + HNO₃ = NOCl + Cl₂ + 2H₂O

Question 23.
What is fuming nitric acid ?
Answer:
Fuming nitric acid : It is brown coloured liquid. It is actually cone. HNO₃ containing dissolved nitrogen dioxide (NO₂) gas. The dissolved nitrogen di­oxide spontaneously comes out of the liquid as brown fumes. That is why, it is called fuming nitric acid.

Preparation of fuming nitric acid : It is prepared by distilling cone, nitric acid with starch or arsenious oxide (As₂O₃).

Property and use of fuming nitric acid : Fuming nitric acid is a stronger oxidising agent than ordinary cone, nitric acid. It is used for many oxidation purposes where ordinary nitric acid does not give satisfactory results.

Question 24.
State the preparation of nitric acid by Ostwald process.
Answer:
Preparation of nitric acid by Ostwald process (1914) :

• In this process ammonia is oxidised in presence of heated (750°C-900°C) platinum gauze catalyst by oxygen in air to produce nitric oxide.
  4NH₃ + 5O₂ = 4NO↑ + 6H₂O + 218,660 cal
• The gases containing nitric oxide (NO) and steam (H₂ are cooled and then mixed with air to oxidise nitric oxide to nitrogen dioxide.
  2NO + O₂ = 2NO₂
• Nitrogen dioxide, is then absorbed in water to yield a 50% solution of nitric acid and nitric oxide.
  3NO₂ + H₂O = 2HNO₃ + NO↑

Question 25.
What are the physical properties of nitric acid ?
Answer:
Physical properties of nitric acid :

• Pure nitric acid is a colourless, fuming liquid of specific gravity 152 at 15°C,
• It boils at 86°C and freezes at -42°C into a transparent crystalline substance.
• It is highly soluble in water.

Question 26.
State the reaction of nitric acid with alkalis.
Answer:
Reaction of nitric acid with alkalis :
As nitric acid is a strong acid, it rapidly reacts with and neutralises alkali to form salt and water.
Equations :
(a) NaOH + HNO₃ = NaNO₃ + H₂O
(b) NH₄OH + HNO₃ = NH₄NO₃ + H₂O

Question 27.
State the reaction of nitric acid with metals.
Answer:
Reaction of nitric acid with metals :
(i) Reaction with iron : Iron is oxidised to ferric nitrate on reacting with hot concentrated nitric acid.
Equation : Fe + 6HNO₃ = Fe(NO₃)₃ + 3NO₂ + 3H₂O

(ii) Reaction with magnesium :

• Cold and moderately concentrated nitric acid on reaction with magnesium produces magnesium nitrate, nitric oxide and water.
  Equation : 3Mg + 8HNO₃ = 3Mg(NO₃)₂ + 2NO + 4H₂O
• Magnesium liberates hydrogen from cold and very dilute nitric acid.
  Equation : Mg + 2HNO₃ Mg(NO₃)₂ + H₂
• Reaction with copper: Hot concentrated nitric acid reacts with copper metal producing copper nitrate and nitrogen dioxide.
  Equation : Cu + 4HNO₃ = Cu(NO₃)₂ + 2NO₂ + 2H₂O

Question 28.
State the oxidising action of concentrated nitric acid.
Answer:
Oxidising action of concentrated nitric acid :
Cone. HNO₃ is a very good oxidising agent.
It oxidises many metals and non-metals.

(i) Cone. HNO₃ oxidises copper turnings to copper nitrate and itself is reduced to brown coloured nitrogen dioxide gas.

(ii) Concentrated HNO₃ oxidises charcoal i.e. carbon to carbon dioxide and is itself reduced to nitrogen dioxide.

Question 29.
What is passive iron?
Answer:
Passive iron: Cold and concentrated nitric acid or fuming nitric acid when comes in contact with iron produces passive iron. Passive iron is chemically inactive.

Cause if passivity : The nibic acid when comes in contact with iron, an insoluble coating of iron oxide (Fe₃O₄) forms on iron at initial stage. The coating makes iron chemically inactive.

Question 30.
What is aqua regia ? What is its use ?
Answer:
Aqua regia : A mixture of cone. HNO₃ (1 vol.) and cone, hydrochloric acid (3 vols.) is known as aqua regia.

Use of aqua regia : It dissolves gold and platinum.

Question 31.
What is ring test experiment of nitric acid ?
Answer:
Ring test experiment of nitric acid : A little amount of dilute nitric acid is taken in a test tube. Freshly prepared ferrous sulphate is added to it. Now cone. H₂SO₄ is taken in another test tube. cone. H₂SO₄ taken in a tube is carefully poured into the above liquid mixture so as to form a heavy layer at the bottom. A brown ring is formed at the junction of two liquids.

Thus, the reaction involved in ring tests as :

Question 32.
State uses of nitric acid.
Answer:
Uses of nitric acid :

• It is used in the production of explosives such as dynamite, gun cotton, nitro-glycerine, picric acid, and trinitro toluene (TNT).
• It is used to prepare aqua regia in electroplating and in battery.
• It is also used to prepare rayon, artificial silk and dyes.

Question 33.
What is acid rain ?
Answer:
Acid rain The oxides NO₂ and SO₂ reacting with moisture and oxygen of air correspondingly produce HNO₃ and H₂SO₄. The acids dissolve in rain water. The rain coming down on earth carrying these acids is known as acid rain. Function of acid rain : The acids present in the rain water damage buildings monuments, statues by corrosion. Soil also becomes acidic which causes degradation of soil that in turn causes decline in forest area and agricultural productivity.

Question 34.
Sulphuric acid is not prepared directly by adding water to SO₃ why ?
Answer:
Explanation : It is because of the fact that water is not used for absorbing SO₃ as the reaction is exothermic. Result is this that large amount of heat evolved will be a cause of most of SO₃ to be volatilised, the rest amount of it does not form any homogeneous mixture but a dense fog of H₂SO₄ particles is formed. H₂SO₄ is not easily available from the fog. Beside this at high temperature some parts of H₂SO₄ decompose to SO₂ and O₂. Hence water is not directly added to SO₃.

Question 35.
What is fumming sulphuric acid or oleum ?
Answer:
Fumming sulphuric acid or oleum : Fumming sulphuric acid or oleum is obtained when SO₃ is passed over 98% (approximately) sulphuric acid.
Equation:

Question 36.
State the effect of SO₂ pollution
Answer:
of SO₂ pollution ;

• SO₂ creates problems in eyes and also in lungs,
• Many diseases like asthama, bronchitis etc. effect if SO₂ is inhaled.

Question 37.
Historical monuments like Tajmahal is also affected by sulphuric acid – why ?
Answer:
Reason : Historical monuments like Tajmahal are damaged due to corrosion when rain carrying H₂SO₄ acid pour on these. Environmentalists say the corrosion of Tajmahal is due to presence of SO₂ in high concentration in the air of Agra. The SO₂ gas emitted from petroleum refinery situated on the other side of the Jamuna river reacts with oxygen and moisture of air to produce H₂SO₄.

Question 38.
What are possible remedies to save our historical monument—Tajmahal?
Answer:
Possible remedy :

• Banning of this factories in the neighbourhood region of Taj and also in Mothura is promulgated by an ordinance.
• Excessive use of motor vehicles should be restricted. Petroleum refining plant should be kept 90 km apart.
• Electrostatic precipitators which are used for treatment of the harmful emitted gas S0₂ before emission.

Question 39.
What is stone cancer ?
Answer:
Stone cancer : In atmosphere, Sulphur dioxide (SO₂) gas reacts with oxygen and water vapour producing sulphuric acid. The acid being dissolved in rain water comes down on marble walls. The marble walls thus corrode, the corrosion of the marble is called stone cancer.

Question 40.
State physical properties of H₂SO₄.
Answer:
Physical properties of H₂SO₄ :

• It is colourless, odourless heavy oily liquid.
• Its specific gravity is 1.84 and its b.p. (boiling point) is 338°C.
• It is soluble in water and it is a corrosive acid.

Question 41.
Water is not added on concentrated sulphuric acid to make it dilute — why ?
Answer:
Explanation : Huge amount of heat is produced if water is added to con­centrated sulphuric acid. As a result water all on a sudden being volatilised spreads all around and creates problem. So, cone. H₂SO₄ acid is slowly added to with constant stirring.

Question 42.
State the reaction of H₂SO₄ with alkalis.
Answer:
Reaction of H₂SO₄ with alkalis : As H₂SO₄ is a dibasic acid containing two replaceable hydrogen atoms, it reacts with bases and alkalis to produce two types of salts acid salts and normal salts and water.
Equation :

Question 43.
State the reaction of H₂SO₄ with carbonates and bicarbonates.
Answer:
Reaction of H₂SO₄ with carbonates and bicarbonates : At ordinary temperature it liberates carbon dioxide from carbonates and bicarbonates.
Equation :

Question 44.
State the reaction of H₂SO₄ with metals.
Answer:
Reaction of H₂SO₄ with metals :
Metals lying above hydrogen in the electrochemical series react with dilute sulphuric acid to form hydrogen gas.
Equation :
(a) Mg + H₂SO₄ = MgSO₄ + H₂↑
(b) Zn + H₂SO₄ = ZnSO₄ + H₂↑

Question 45.
State the oxidising property of concentrated sulphuric acid.
Answer:
Oxidising property of concentrated sulphuric acid :
(a) Reaction with metals : Hot and concentrated sulphuric acid oxidises metallic copper, silver, zinc etc. into their sulphates, itself being reduced to sulphur dioxide.
Equation :

(b) Reaction with non-metals Non-metals carbon and sulphur on being treated with hot concentrated sulphuric acid are oxidised to carbon dioxide, sulphur dioxide respectively.
Equation :

Question 46.
State the dehydration action of concentrated sulphuric acid.
Answer:
Dehydration action of concentrated sulphuric acid :
(a) Concentrated sulphuric acid chars sugar. The acid takes up all its hydrogen and oxygen in the form of water molecules from the compound separating black carbon as residue.
Equation :

(b) When a mixture of formic acid and concentrated sulphuric acid is heated carbon monoxide is produced by loss of water molecule from the formic acid.

Equation

Question 47.
What is the identification reaction of sulphuric acid ?
Answer:
Identification reaction of sulphuric acid : When barium chloride solution is added to dilute sulphuric acid, a white precipitate of barium sulphate insoluble in dilute or concentrated hydrochloric acid or nitric acid is obtained.
Equation :

Question 48.
State the uses of sulphuric acid.
Answer:
Uses of sulphuric acid :

• It is used for the preparation of different chemical compounds like HCl, HNO₃, ether, alcohol etc.
• It is used as an important raw material for dyes, medicine, plastic industries.
• It is used to prepare different explosives like trinitrotoluene (TNT) nitroglecer- ine etc.

Question 49.
Explain the following :
Concentrated nitric acid turns yellow in sun light.
Answer:
Explanation Nitric acid turns yellow because of its decomposition forming nitrogen dioxide (NO₂gas.
Equation : 4HNO₃= 4NO₂+ 2H₂O + O₂

Broad Answer Type Questions

Question 1.
State the contact process for the manufacture of sulphuric acid.
Answer:
Contact process for the manufacture of sulphuric acid :
Principle : (a) Formation of SO₂: SO₂ is prepared by burning sulphur or iron pyrites in excess of air.

(b) Formation of Sulphur trioxide (SO₃) SO₃ is prepared by the oxidation of sulphur dioxide with oxygen (from air) in presence of platinised asbestos or, V₂O₅ as catalyst at 450°C.
Equation:

(c) Formation of oleum : Now sulphur trioxide thus produced are not allowed to react with water directly. Sulphur trioxide absorbs concentrated sulphuric acid (98%) turning it as fumming sulphuric acid or oleum.
Equation :

(d) Dilution of oleum to sulphuric acid : Pure and concentrated sulphuric acid is produced by adding slowly requisite amount of water in fumming sulphuric acid.
Equation : H₂S₂O₇ + H₂O = 2H₂SO₄

Question 2.
State an experiment to illustrate the solubility of HCl in water and the acidic character of the aqueous solution.
Answer:
Fountain experiment : A round bottomed flask is fitted with a cork through which passes a long tube ending in a jet in­side the flask. The flask is filled with hydrogen chloride and clamped in an inverted position so that the other end of the tube dips in water coloured blue by litmus.

The flask is then cooled when the gas contracts inside. As a result, the blue solution rises up through the tube and enters the flask in the form of fountain. The blue litmus solution in the flask turns red. This experiment proves simultaneously the solubility of hydrogen chloride in water and the acidic character of its aqueous solution.

Detailed explanations in West Bengal Board Class 10 Physical Science Book Solutions Chapter 3 Chemical Calculations offer valuable context and analysis.

WBBSE Class 10 Physical Science Chapter 3 Question Answer – Chemical Calculations

Very Short Answer Type Questions

Question 1.
What is the molecular weight of ammonium phosphate ?
Answer:
149

Question 2.
How much CaO is obtained from 10 kg CaCO₃ ?
Answer:
5.6 kg

Question 3.
How much CaCO₃ will react with dil HCl to produce 22 g CO₂ ?
Answer:
50 g

Question 4.
How much hydrogen is required to produce 72 g water?
Answer:
8g

Question 5.
How much potassium chlorate is to be heated to produce as much oxygen as required to burn 6 g carbon completely?
Answer:
40.83 g

Question 6.
How much quantity of silver chloride (AgCl) can be obtained from 1.0 g silver nitrate?
Answer:
0.844 g

Question 7.
How many grams limestone are needed to get 48g CO₂ ?
Answer:
109.09 g

Question 8.
How much hydrogen is produced when steam is passed over 28 kg red hot iron?
Answer:
1.33 kg

Question 9.
What is mole number of a substance ?
Answer:
Mole number of a substance

Question 10.
What is the percentage of water in blue vitriol ?
Answer:
36.07%.

Question 11.
2 Mg + O₂ = 2 MgO; what type of chemical reaction is it?
Answer:
2 Mg + O₂ = 2 MgO is direct combination type of chemical reaction.

Question 12.
HCl + NaOH = NaCl + H₂ O; what type of chemical reaction is it?
Answer:
HCl + NaOH = NaCl + H₂ O is the type of neutralisation reaction.

Question 13.
Zn + CuSO₄ = ZnSO₄ + Cu; what type of chemical reaction is it?
Answer:
Zn + CuSO₄ = ZnSO₄ + Cu is the type of substitution reaction.

Question 14.
NH₄ CNO (8) CO(NH₂)₂; what type of chemical reaction is it?
Answer:
NH₄ CNO arrow CO(NH₂)₂ is the type of rearrangement reaction.

Question 15.
Give an example of double decomposition type of reaction.
Answer:
AgNO₃ + NaCl = AgCl + NaNO₃ is an example of double decomposition type of reaction.

Question 16.
State a limitation of a chemical equation.
Answer:
A reaction whether exothermic or endothermic is not known from a chemical equation.

Question 17.
Give an example of addition reaction.
Answer:
Carbon monoxide reacts with chlorine to form carbonyl chloride (COCl₂) is an example of addition reaction.

Question 18.
Give an example of a substitution reaction.
Answer:
Chlorine reacts with methane (CH₄) to form successively CH₃ Cl, CH₂ Cl₂, CHCl₃ and ultimately CCl₄ in presence of sunlight is an example of a substitution reaction.

Question 19.
Give an example of a thermal decomposition type of reaction.
Answer:
Calcium carbonate on heating decomposes into calcium oxide and carbon dioxide is an example of a thermal decomposition type of reaction.

Question 20.
Give an example of redox type of reaction.
Answer:

is an example of redox type of reaction.

Question 21.
Balance the following reaction: Fe + H₂ O(Fe₃ O₄ + H₂.
Answer:
Balanced equation of Fe + H₂ O arrow Fe₃ O₄ + H₂ is
3 Fe + 4 H₂ O = Fe₃ O₄ + 4 H₂

Question 22.
2 SO₂ + O₂ ⇌ 2 SO₃; what type of reaction is it ?
Answer:
2 SO₂ + O₂ ⇌ 2 SO₃ is an example of reversible type of reaction.

Question 23.
A + B²⁺ = A²⁺ + B; what type of reaction is it ?
Answer:
A + B²⁺ = A²⁺ + B is an example of oxidation-reduction type of reaction.

Question 24.
Balance the following reaction :
MnO₂ + HCI → MnCI₂ + CI₂ + H₂O
Answer:
Balanced equation of MnO₂ + HCl → MnCl₂ + Cl₂ + H₂O is
MnO₂ + 4 HCl = MnCl₂ + Cl₂ + 2 H₂O

Question 25.
Balance the following reaction :
Ag₂ SO₄ + BaCI₂ → BaSO₄ + AgCl.
Answer:
Balanced equation of Ag₂ SO₄ + BaCl₂ → BaSO₄ + AgCl is
Ag₂ SO₄ + BaCl₂ = BaSO₄ + 2 AgCl

Question 26.
Write the equation relating energy with mass.
Answer:
E = m c²

Question 27.
Write the relation between molecular mass and vapour density.
Answer:
Molecular mass = 2 × Vapour density.

Question 28.
Calculate the vapour density of oxygen relative to hydrogen.
Answer:
Vapour density of oxygen
= \(\frac{Molecular mass of oxygen}{2} = [latex]\frac{32}{2}\) = 16

Question 29.
6 g carbon on complete combustion produce how much volume of CO₂ at STP ?
Answer:

12g carbon on complete combustion produce 22.4 L CO₂ at STP
6g carbon on camplete combustion produce 11.2 L CO₂ at STP

Question 30.
One mole of zinc reacts with excess H₂ SO, to produce how many moles of hydrogen ?
Answer:
1 mole of hydrogen.

Short Answer type Questions :

Question 1.
What is empirical formula?
Answer:
Empirical formula : It is the formula of a compound which gives the simple whole number ratio of the atoms of various elements present in one molecule of compound.

Question 2.
What is molecular formula ?
Answer:
Molecular formula : It is the formula of a compound which gives the actual number of atoms of various elements present in one molecule of the compound.

Question 3.
What are the limitations of chemical formula ?
Answer:
Limitations of chemical formula :

1. It fails to convey whether the elements in a molecule are present in the form of atoms or ions.
2. It does not tell anything about the binding force that holds atoms in a molecule together.
3. It does not tell us about the arrangement of various atoms with respect to one another within the molecule.

Question 4.
What is structural formula ?
Answer:
Structural formula : A formula which gives the actual arrangement of the different atoms in the molecule or show how the different atoms in the molecule are linked together is called a structural or a graphic formula of the compound.

Question 5.
What is percentage of an element?
Answer:
Percentage of an element : Percentage of an element in a chemical compound is the number of parts by weight of it present in 100 parts by weight of the compound.

Question 6.
What are mass-mass relationship problems ?
Answer:
Mass-mass relation hip problems : In this type of problems, mass of one of the reactants/products is to be calculated if that of the other reactants/ products is to be calculated if that of the other reactants/ products are given.

Question 7.
What are mass-volume relationship problems ?
Answer:
Mass-volume relationship problems : In this type of problems, mass or volume of one of the reactants or products is calculated from the volume or mass of other substances.

Question 8.
What are volume-volume relationship problems ?
Answer:
Volume-volume relationship problems : In this type of problems, the volume of one of the reactants or products is to be calculated from the volume of some other reactant and product.

Question 9.
What is limiting reactant ?
Answer:
Limiting reactant : The reactant which is completely used and determines the amount of product formed is known as limiting reactant.

Question 10.
What is theoretical yield ?
Answer:
Theoretical yield : The theoretical yield of a product is the maximum yield obtainable as calculated on the basis of the amount of limiting reactant used.

Question 11.
What is percent yield?
Answer:
Percent yield : Percent yield which is the ratio of the actual yield to the theoretical yield multiplied by 100 .

Question 12.
What do you mean by chemical reaction ?
Answer:
Chemical reaction: Any chemical change in matter which involves the transformation of matter into a new substance or new substances is termed as chemical reaction.

Question 13.
Define reactants in a chemical reaction.
Answer:
Reactants: The substances with which a chemical reaction is started are called the reactants.

Question 14.
Define products in a chemical reaction.
Answer:
Products: The substances formed as the result of the chemical reaction are called the products.

Question 15.
Define direct combination reaction.
Answer:
Direct combination : The reaction in which two or more reactions combine directly forming molecules of new substance is called direct combination.
Example : Burning magnesium wire reacts directly with oxygen forming new molecules of magnesium oxide.
2 Mg + O₂ = 2 MgO

Question 16.
What is meant by decomposition reaction?
Answer:
Decomposition : When molecule of a substance is broken down or decomposed in a chemical reaction to form two (or more) new substances in presence of heat or electricity. It is called decomposition.
Example : (a) Calcium carbonate on heating decomposes into calcium oxide and carbon dioxide.

(b) Electricity is passed through acidulated water hydrogen and oxygen are produced due to decomposition of water.
2H₂O = 2H₂ + O₂

Question 17.
Define double decomposition reaction.
Answer:
Double decomposition : The reaction in which the constituents of the molecules of reactants Change their position and forming molecules of new substances is called double decomposition.
Example : AgNO₃ + NaCl = AgCl↓+ NaNO₃

Question 18.
What is meant by acid-base reaction or neutralisation reaction ?
Answer:
Acid-base reaction or neutralisation reaction : In this reaction an acid reacts with a base forming salt and water. Equivalent amount of an acid neutralises an equivalent amount of a base. This is known as neutralisation reaction.

Question 19.
Define oxidation-reduction type reaction.
Answer:
Oxidation-reduction reaction : The chemical reaction in which a chemical species loses electron(s) is an oxidation reaction and the reaction in which a chemical species gains electron(s) is called oxidation-reduction reaction.

Question 20.
What is meant by addition reaction?
Answer:
Addition reaction: The reaction in which one reactant molecule directly combines with other molecule of reactant forming new molecules of product without leaving any part of molecules of reactants is known as addition reaction.

Question 21.
Define substitution reaction.
Answer:
Substitution reaction: It is a chemical reaction in which one atom or molecule of a compound is replaced by another atom or molecule of another substance.
Example : Zn + CuSO₄ = ZnSO₄ + Cu

Question 22.
What is meant by rearrangement reaction?
Answer:
Rearrangement reaction: A reaction where a compound changes by internal arrangement of its atoms into another substance with different properties but having the same composition is known as rearrangement reaction.
Example : Ammonium cyanate changes to urea on heating.

Question 23.
Define chemical equation.
Answer:
Chemical equation : A brief representation of a chemical reaction by using symbols of atoms of the elements and formulae of molecules of reactants and products maintaining the balance in between is known as chemical equation. It reveals both the qualitative ancL quantitative aspects of a chemical change.

Broad Answer Type Questions :

Question 1.
What steps should be followed to solve a problem based on chemical equation by weight-weight method ?
Answer:
Following steps are followed :

1. First write down the complete balanced chemical equation.
2. The molecular weight of the reactants and products are to be calculated from their respective formulae by adding atomic weights of the concerned elements.
3. The unknown weight of the substance asked for in the question is to be calculated from the calculated weight in the equation.
4. Same units are to be used for all quantities.

Question 2.
What are the informations avallable from the formula CaCO₃ ?
Answer:
The formula CaCO₃ conveys the following informations :

1. It stands for calcium carbonate.
2. It tells that calcium carbonate is composed of calcium, carbon and oxygen elements.
3. It represents that a molecule of calcium carbonate.
4. It represents that a molecule of calcium carbonate is made up of One atom each of calcium and carbon and three atoms of oxygen.
5. It stands for 100 parts by weight of calcium carbonate i.e. its molecular weight and signifies that the ratio of calcium, carbon and oxygen by weight in it is 40: 12: 48.

Question 3.
What is the method of writing chemical equation ?
Answer:
Method of writing chemical equation :
i. Initially the symbols of atoms of elements and formulae of molecules of reactants and products are written.

ii. Symbols and formulae of the reactants are written in the left side and these for products are in the right side. An arrow mark (→) is placed between reactants and products. For more than one reactants and products a plus sign (+) is to be given between the reactants and also between the products.

iii. Number of atoms of the reactants in the left hand side must be equal to the number of atoms of the products in the right hand side so as to maintain the law of conservation of mass. To equalise both sides, proper multiplication is required so that the number of atoms in both sides are same.

iv. Now the equation is expressed by replacing the arrow sign by a sign of equal ( = ).

Question 4.
What informations are obtained from the chemical equations ?
Answer:
A chemical equation gives the following informations :
(a) Qualitative informations :

• From chemical equation, the naming of elements and compounds taking part in the reaction and also the products are known.
• From chemical equation, the symbols and the formulae of the reactants and products are also known.

(b) Quantitative informations :

• Number of atoms or molecules of the reactants and products involved in the reaction are known.
• How many parts of elements and compounds taking part in the reaction and producing are also known.
• If the reactants and products are all gaseous then at the same temperature and pressure the ratio in volumes is known.

Question 5.
What informations are obtained from the equation :
C + O₂ = CO₂
Answer:
The following informations are obtained from the equation :
C + O₂ = CO₂

(a) Qualitative informations :
i. From the above equation it is known that carbon combines with oxygen producing carbon dioxide.
ii. Their respective symbols and formulae are also known.

(b) Quantitative informations :
i. One carbon atom combines with one oxygen molecule producing one carbon dioxide molecule.
Hence total number of atoms in the left hand side is (1 + 2) = 3 and the number of atoms in the right hand side is also 3.
ii. One gram-atom carbon reacts with one gram-molecule of oxygen giving rise one gram-molecule of carbon dioxide.
12 g carbon combines with 32 g oxygen yield 44 g carbon dioxide.
Hence, total mass in the left hand side (12 + 32) g = 44 g is equal to the total mass in the right hand side 44 g. It proves law of conservation of mass.
iii. Again 12 g carbon combines with 32 g oxygen producing 22.4 litre of carbon dioxide at STP.

Question 6.
What informations are obtained from the equation :
2 H₂ + O₂ = 2 H₂O
Answer:
The following informations are obtained from the equation :
2 H₂O + O₂ = 2 H₂O

(a) Qualitative informations : The reactants are hydrogen and oxygen, water is the product.
(b) Quantitative informations :

1. Two molecules of hydrogen combine with one molecule oxygen to produce two molecules water.
2. Two volumes hydrogen and one volume oxygen combine to produce two volumes water at the same temperature and pressure and their ratio is 2 : 1 : 2
3. Two moles of hydrogen and one mole oxygen combine chemically to produce two moles water.

Question 7.
What informations are obtained from the equation :
3 H₂ + N₂ = 2 NH₃
Answer:
The following informations are obtained from the equation :
3 H₂ + N₂ = 2 N H₃
(a) Qualitative informations : The reactants are hydrogen and nitrogen, ammonia is the product.
(b) Quantitative informations :

1. Three molecules of hydrogen combine with one molecule nitrogen to produce two molecules ammonia.
2. Three volumes hydrogen and one volume nitrogen combine to produce two volumes ammonia at the same temperature and pressure and their ratio is 3 : 1 : 2.
3. Three moles of hydrogen and one mole nitrogen combine chemically to produce two moles ammonia.

Question 8.
What are the limitations of a chemical equation ?
Answer:
Limitations of a chemical equation :

1. Under what conditions a chemical reaction is occurred i.e. pressure, temperature, catalyst are not known.
2. A reaction whether exothermic or endothermic is not known from chemical equation.
3. Chemical equation cannot provide information about completion of the reaction or attainment of equilibrium.
4. A chemical equation does not give any idea about the reversibility of the reaction.
5. From a chemical equation, the time required for the completion of the equation is not known.
6. A reaction whether slow or fast does not know from the equation.
7. Equation does not provide information regarding the nature of the reactants and products viz. solid, liquid or gas.

Question 9.
What is meant by ‘balancing’ of a chemical equation ? Why it is necessary?
Answer:
Balancing of a chemical equation : It means making both the sides of the equation equal in respect of the kind and number of the atoms of the elements involved.
Balancing of a chemical equation is necessary : Due to the conservation of mass and indestructibility of matter, no atoms can be created or destroyed in a chemical reaction. Hence, the same kind of atoms in same numbers must be present in both the sides of the chemical equation.

Question 10.
Explain the method of balancing a chemical equation by trial and error method.
Answer:
Balancing of a chemical equation by trial and error method :
(i) In this method the proper numbers are putting before reactants and products so that the number of atoms in both sides are equal.
(ii) In doing so, we must cautious to see that all the reactants and products exist as molecules, and not as atoms, as free existence of atoms is not possible.

Question 11.
Balance the equation KClO₃ ⟶ KCl + O₂ by trial and error method.
Answer:
KClO₃ ⟶ KCl + O₂; it is seen that the number of atoms of oxyen in left hand side is 3 whereas in the right hand side it is 2. To equalize the number of atoms of oxygen in both sides it requires to multiply KClO₃ by 2 and oxygen by 3.
2 KClO₃ ⟶ KCl + 3 O₂. So as to balance this equation if KCl is multiplied by 2 then the equation is properly balanced.
2 KClO₃ = 2 KCl + 3 O₂

Question 12.
Write the following as balanced equations.
(i) Cu + HNO₃ ⟶ Cu(NO₃)₂ + NO + H₂ O
(ii) Pb(NO₃)₂ ⟶ PbO + NO₂ + O₂
(iii) Al + NaOH + H₂ O ⟶ NaAlO₂ + H₂
(iv) CuO + NH₃ ⟶ Cu + N₂ + H₂ O
Answer:
Balanced equations are :
(i) 3 Cu + 8 HNO₃ = 3 Cu(NO₃)₂ + 2NO + 4H₂ O
(ii) 2 Pb(NO₃)₂ = 2 PbO + 4 NO₂ + O₂
(iii) 2 Al + 2 NaOH + 2 H₂ O = 2 NaAlO₂ + 3H₂
(iv) 2 NH₃ + 3 CuO = 3 Cu + 2 N₂ + 3H₂O

Numerical problems :

Working formula :

(i) Molecular weight (M) = n × Emperical formula
(ii) Atomic weight of a gaseous element = \(\frac{\text { Actual yield }}{\text { Theoretical yield }} \times 100\)
Problems related to mass-mass relationship

Example 1:
How many grams of oxygen evolve when 122.5 g potassium chlorate is heated ? (Given, K = 39, Cl = 35.5, O = 16)
Answer:
The balanced equation is :
2 KClO = 2 KCl + 3 O₂
2[39 + 35.5 + 3 × 16] g & 3[2 × 16] g
= 245 g = 96 g
By heating 245 g KClO₃ 96 g O₂ is obtained
∴ By heating 122.5 g KClO₃ \(\frac{96 \times 122.5}{245}\) = 48 g O₂ is obtained

Example 2:
2.6 g zinc is treated with excess dil H₂ SO₄; how many gram oxygen combines with the evolved hydrogen?
Answer:
The balanced equation for production of hydrogen is :
Zn + H₂ SO₄ = ZnSO₄ + H₂
65g (2 × 1) g = 2g
So, 65 g zinc produces 2 g hydrogen
∴ 2-6 zinc produces \(\frac{2 \times 2.6}{65} \mathrm{~g}\) = 0.089 g hydrogen
Now, the reaction where hydrogen and oxygen combine is :
2 H₂ + O₂ = 2 H₂ O
So, 4 g hydrogen combine with 32 g oxygen 0.08 g hydrogen combine with \(\frac{32 \times 0.08}{4} \mathrm{~g}\) = 0.64 g oxygen

Example 3:
What is the observed loss in weight of 5 g calcium carbonate when it undergoes thermal decomposition?
Answer:
The balanced equation is :
CaCO₃ = CaO + CO₂
(40 + 12 + 16 × 3)g (12 + 16 × 2)g
= 100g = 44g
Loss in weight in the weight of CO₂ that escapes
100 g CaCO₃ produces 44g CO₂
∴ 5 g CaCO₃ produces \(\frac{44 \times 5}{1000}\) g = 2.2g CO₂

Example 4:
What is the percentage of ammonia in that quantity of ammonium chloride that can produce 5g ammonia?
Answer:
The balanced equation of reaction is :
2 NH₄ Cl + CaO = 2 NH₃ + CaCl₂ + H₂ O
2[14 + 1 × 4 + 35.5] g 2[14 + l × 3] g
= 107 g = 34 g
So, 34 g ammonia is obtained form 107 g NH₄ Cl

Example 5:
What weight of potassium chlorate of 96% purity will yield 4.8 g oxygen on complete thermal decomposition?
(Given, K = 39, Cl = 35.5, O = 16)
Answer:
The balanced equation is :
2 KClO₃ = 2 KCl + 3 O₂
245 g 96 g
∴ 96 g oxygen is obtained from 245 g KClO₂ of 100% purity
∴ 4.8 g oxygen is obtained from \(\frac{245 \times 4 \cdot 8}{96}\) g
= 12.25 g KClO₃ of 100% purity.
Let x gram of 96% purity contains 12.25 g KClO₃ of 100% purity
∴ \(\frac{96}{100}\).x = 12.56
or, x = \(\frac{12 \cdot 25 \times 100}{96}\) = 12.76 (approx)
So, the required quantity of KClO₃ = 12.76g

Example 6:
On strong heating limestone decomposes into quicklime and carbon dioxide. How much quantity of limestone will produced on complete decomposition, 30 g of quicklime by the above reaction?
Answer:
The balanced equation is :
CaCO₃ = CaO + CO₂
[40 + 12 + 3 × 16] g [40 + 16] g
= 100 g = 56 g
So, 56 g CaO is obtained by the complete decomposition of 100 g CaCO₃
∴ 30 g CaO is obtained by the complete decomposition of
\(\frac{100 \times 30}{56}\)g = 53.6 g CaCO₃
Thus 53.6 g limestone will have to be decomposed.

Example 7:
How many grams of magnesium metal will give 1.2 g hydrogen on complete reaction with dilute H₂ SO₄ (Mg = 24, H = 1)
Answer:
The balanced equation is :
Mg + H₂ SO₄ = MgSO₄ + H₂
24 g (1 × 2) g = 2 g
So, 2 g H₂ is obtained from 24 g Mg
∴ 1.2 g H₂ is obtained from \(\frac{24 \times 1.2}{2}\)g Mg = 14.4 g Mg
So, 14.4 g Mg will be required.
Problems based on mass-volume relationship

Example 8:
What volume of carbon dioxide measured at 300 K and 720 mm pressure be obtained on treatment of 1 g CaCO₃ with dilute HCl ?
Answer:
The balanced equation is :
CaCO₃ + 2 HCl = CaCl₂ + H₂O + CO₂
1 mol(40 + 12 + 3 × 16) g        1 mol (22.4 lit at NTP)
= 100 g
So, 100g CaCO₃ gives 22.4 lit CO₂ at NTP
1g CaCO₃ gives 0.224 lit CO₂ at NTP

Reducing the volume to the given condition applying gas equation,

P₁ = 760 mm
V₁ = 0.224 lit
T₂ = 273 K
P₂ = 720 mm
V₁ = ?
T₂ = 300 K

= 0-2598 lit = 259-8 ml
Hence, 259.8 ml CO₂ will be obtained at 300 K and 720 mm pressure on treatment of 1 g CaCO₃ with HC 1.

Example 9:
How much potassium nitrate should be heated to get enough oxygen required to completely burn 56 lit of hydrogen at NTP ?
Answer:
The balanced equation is :

= 2 × 22-4 lit
= 44.8 lit (at NTP)
So, 44.8 lit H₂ requires 22.4 lit O₂ at NTP
56 lit H, requires \(\frac{2 \cdot 24 \times 56}{44 \cdot 8}\) at NTP
= 28 lit O₂ at NTP

The other balanced equation is :

= 202 g
Now, 22.4 lit O₂ at NTP are obtained by heating 202 g KNO₃
∴ 28 lit O₂ at NTP are obtained by heating \(\frac{202}{22.4}\) × 28 g KNO₃
= 252.5 g KNO₃

Problems based on volume-volume relationship.

Example 10:
In the Ostwald process for the manufacture of nitric acid, ammonia gas is burnt in oxygen in the presence of a pt-catalyst. What volume of O₂ is required and what volume of NO is formed in the combustion of 500 lit of NH₃.
Answer:
The balanced equation is :

(i) 4 lit of NH₃ requires 5 lit of O₂ for combustion
500 lit of NH₃ requires \(\frac{5 \times 500}{4}\) lit = 625 lit O₂
(ii) 4 lit of NH₃ produces 4 lit NO
∴ 500 lit of NH₃ produces \(\frac{4}{4}\) × 500 lit NO = 500 lit NO

Example 11:
Calculate the volume of oxygen necessary to burn completely 5 lit butane gas. What is the volume of carbon dioxide formed?
Answer:
The balanced equation is :

So, 2 lit of butane at NTP requires 13 lit O₂ at NTP
∴ 5 lit of butane at NTP requires \(\frac{13 \times 5}{2}\) lit = 32.5 lit of O₂ at NTP.
Also 2 lit of butane at NTP produce 8 lit CO₂ at NTP
∴ 5 lit of butane of NTP produce
= \(\frac{8}{2}\) × 5 lit = 20 lit CO₂ at NTP

West Bengal Board Class 10 Physical Science Notes WBBSE

1. Concerns About Our Environment Class 10 WBBSE Notes
2. Behaviour of Gases Class 10 WBBSE Notes
3. Chemical Calculations Class 10 WBBSE Notes
4. Thermal Phenomena Class 10 WBBSE Notes
5. Light Class 10 WBBSE Notes
6. Current Electricity Class 10 WBBSE Notes
7. Atomic Nucleus Class 10 WBBSE Notes
8. Physical and Chemical Properties of Matter Class 10 WBBSE Notes
   • Chapter 8.1 Periodic Table and Periodicity of the Properties of Elements Class 10 WBBSE Notes
   • Chapter 8.2 Ionic and Covalent Bonding Class 10 WBBSE Notes
   • Chapter 8.3 Electricity and Chemical Reactions Class 10 WBBSE Notes
   • Chapter 8.4 Inorganic Chemistry in the Laboratory and in Industry Class 10 WBBSE Notes
   • Chapter 8.5 Metallurgy Class 10 WBBSE Notes
   • Chapter 8.6 Organic Chemistry Class 10 WBBSE Notes

WBBSE Class 10 Solutions

Detailed explanations in West Bengal Board Class 10 Physical Science Book Solutions Chapter 8.5 Metallurgy offer valuable context and analysis.

WBBSE Class 10 Physical Science Chapter 8.5 Questionuestion Answer – 8.5 Metallurgy

Very Short Answer Type Questions

Question 1.
Which metal is present in the earth’s crust in largest percentage ?
Answer:
Aluminium.

Question 2.
What is stainless steel ?
Answer:
Stainless steel is an alloy of iron with chromium and nickel.

Question 3.
What is the purpose of galvanising an article ?
Answer:
The purpose of galvanising an article to protect the article from corrosion.

Question 4.
What is the action of alkali on iron ?
Answer:
Iron does not react with any alkali.

Question 5.
How hydrogen gas may be prepared using aluminium ?
Answer:
Hydrogen gas may be prepared by boiling aluminium powder with alkali.

Question 6.
What is the basic component of chuni (ruby), panna (emarald) etc.?
Answer:
The basic component of chuni and panna is Al₂O₃.

Question 7.
What is an ore ?
Answer:
Ores are the minerals from which the metals can be extracted conveniently and profitably.

Question 8.
Name a metal that reacts both with an acid and alkali to produce salt and hydrogen.
Answer:
Zinc or Aluminium.

Question 9.
Name the chief ore of Zinc and write down its formula.
Answer:
The chief ore of Zinc is Zinc blende. Formula of zinc blende ZnS

Question 10.
Burning of which metal cannot be extinguished with CO₂ gas ?
Answer:
Burning of magnesium cannot be extinguished with CO₂ gas.

Question 11.
Which metals are present in brass ?
Answer:
Copper and Zinc are present in brass.

Question 12.
Name an alloy of magnesium.
Answer:
Electron is an alloy of magnesium.

Question 13.
Which type of iron is used in the core of an electromagnet ?
Answer:
Soft iron is used in the core of an electromagnet.

Question 14.
Which metal is commonly used for galvanisation ?
Answer:
Zinc is commonly used for galvanisation.

Question 15.
Name a metal that produces amphotaric oxide.
Answer:
Aluminium or Zinc produces amphoteric oxide.

Question 16.
Name two metals which do not react with alkali.
Answer:
Copper, iron do not react with alkali.

Question 17.
Which metal can produce hydrogen from dilute nitric acid ?
Answer:
Magnesium can produce hydrogen from dilute nitric acid.

Question 18.
Name the chief ore of magnesium.
Answer:
The chief ore of magnesium is Magnesite (MgCO_s).

Question 19.
Name the principle ore of aluminium.
Answer:
The principle ore of aluminium is Bauxite (Al₂O₃, 2H₂O),

Question 20.
Name two alloys of aluminium.
Answer:
Two alloys of aluminium are :

• Duralumin
• Aluminium bronze

Question 21.
What is metallurgy ?
Answer:
Metallurgy is the process of extracting metals from their ores.

Question 22.
What is gangue ?
Answer:
Gangue or matrix are the rocky and earthly impurities associated with the minerals.

Question 23.
What is slag ?
Answer:
Slag is the light and fusible material obtained by the combination of flux with gangue.

Question 24.
What is Flux ?
Answer:
Flux is the substance which combines with gangue to form light and easily fusible material called slag.

Question 25.
What is thermite ?
Answer:
Thermite is the mixture of metal oxide and the aluminium powder.

Question 26.
What is amalgamation ?
Answer:
Amalgamation is the process in which finely powdered ore is brought into contact with mercury which combines in the ore to form amalgam.

Question 27.
Why alkali metals are not found in free state in nature ?
Answer:
Due to high reactivity, alkali metals do not occur free in nature.

Question 28.
What is called fusion mixture ?
Answer:
A mixture of Na₂CO₃ and K₂CO₃ is called fusion mixture.

Question 29.
What is Black ash ?
Answer:
Mixture of Na₂CO₃ and CaS is called black ash.

Question 30.
What is Lime light ?
Answer:
On heating in oxy-hydrogen flame, lime becomes incandescent and emits bright white light, called lime light.

Question 31.
What is American baking powder ?
Answer:
Pure Ca(H₂PO₄)₂ is used as American baking powder.

Question 32.
What is the use of MgSO₄, 7H₂O?
Answer:
MgSO₄, 7H₂O is used as a purgative in medicine.

Question 33.
What is Hydrolith ?
Answer:
Calcium hydride is known as hydrolith.

Question 34.
What is the constituent of bones and teeth ?
Answer:
Calcium phosphate is the constituent of bones and teeth.

Question 35.
What is the most abundant metal next to aluminium ?
Answer:
Iron is the most abundant metal, next to aluminium.

Question 36.
What is Cementite ?
Answer:
Iron carbide (Fe₃C) is known as cementite.

Question 37.
What is Green vitriol ?
Answer:
FeSO₄,7H₂O is called green vitriol.

Question 38.
What is called Mohr’s salt ?
Answer:
FeSO₄,(NH₄)₂SO₄, 6H₂O is called Mohr’s salt.

Question 39.
What is Kipp’s base ?
Answer:
Mixture of FeS + H₂SO₄ is called Kipp’s base.

Question 40.
What is Invar ?
Answer:
Invar is an alloy of steel containing 36% nickel.

Question 41.
What is Spiegeleisen ?
Answer:
Spiegeleisen is an alloy of iron, manganese and carbon used in steel making.

Question 42.
What is Matte ?
Answer:
Matte contains Cu₂S + FeS.

Question 43.
What is Blister Copper ?
Answer:
Blister Copper contains (96 -98)% copper with small amounts of Ag and Au as impurity.

Question 44.
What is called Fool’s gold ?
Answer:
CuFeS₂ is called Fool’s gold.

Question 45.
What Nila thotha ?
Answer:
Blue vitriol (CuSO₄, 5H₂O) is called ‘Nila thotha’.

Question 46.
What is Bordeaux mixture?
Answer:
Mixture of CuSO₄ solution and lime called Bordeaux mixture is used as fungicide.

Question 47.
What is Philosopher’s wool ?
Answer:
Zinc oxide is called philosopher’s wool, zinc white or Chinese white.

Question 48.
What is the nature of ZnO ?
Answer:
ZnO being amphoteric in nature dissolves both in acids and alkalis.

Question 49.
What is Lithopone ?
Answer:
Lithopone (ZnS + BaSO₄) is used as white paint.

Question 50.
What is the use of ZnS ?
Answer:
ZnS is used for preparing luminous dials for watches and X-ray screens.

Question 51.
What is German silver ?
Answer:
German silver is an alloy of Cu (60%), Zn (20%) and Ni (20%). It does not contain silver.

Question 52.
What is White vitriol ?
Answer:
Zinc sulphate hepta hydrate (ZnSO₄, 7H₂O) is called white vitriol

Question 53.
Which metal is common in both bell metal and bronze?
Answer:
Bell metal and bronze are both allloys of copper and tin.

Question 54.
What is the non metallic component present in stainless steel?
Answer:
The non-metallic component of stainless steel is carbon (c).

Question 55.
What is the reason behind Wilson’s disease?
Answer:
This occurs due to abnormal metabolism of copper and as a result, free copper in the plasma enters different tissues, binds with proteins and gets deposited in liver, kidney and brain.

Question 56.
Write the chemical reaction involved in thermite process.
Answer:
The chemical reaction involved is as follows :
Fe₂O₃ + 2Al → 2Fe + Al₂O₃ + heat

Question 57.
What is anodizing ?
Answer:
Anodizing is a process by which a thick, protective layer of aluminium oxide is applied on the aluminium metal surface to protect it from corrosion.

Question 58.
Why does a new aluminium vessel lose its shine?
Answer:
In presence of air, a thin layer of aluminium oxide is formed on the surface of metallic aluminium. So, the aluminium vessel loses its shine.
4Al + 3O₂ = 2Al₂O₃

Question 59.
What is the principle behind extracting less reactive metals?
Answer:
Metals with less reactivity are extracted by heating their oxides.

Question 60.
What is the principle behind extracting highly reactive metals?
Answer:
Metals of high reactivity are extracted by the electrolytic reduction of their molten chlorides or oxides. During electrolysis, the pure metal is produced at the cathode.

Question 61.
What is the principle behind extracting moderately reactive metals?
Answer:
Metals which are moderately reactive are extracted by reduction of their oxides with carbon (or zinc or iron etc.)

Question 62.
Rusting is a redox process. What is the oxidation reaction?
Answer:
The oxidation process is the oxidation of metallic ion to Fe²⁺ and finallly to Fe³⁺ ion occurring at the anode.

Short Answer Type Questions:

Question 1.
Concentrate Nitric acid can be kept in vessel made of aluminium why?
Answer:
Reason Concentrate Nitric acid does not react with aluminium, so it can be kept in aluminium vessel.

Question 2.
Should we take or not ‘pickle’ wrapped to aluminium foils ?Give reasons.
Answer:
Reason : Pickle contain organic acetic acid known as vinegar, which reacts with aluminium foil to produce aluminium salts which are harmful to our health. So pickle’s wrapped in aluminium foils should be taken.

Question 3.
What happens when a spoon made of iron is introduced in acidified CuSO₄ solution ?
Answer:
Explanation : Spoon made of iron reacts with acidified CuSO₄ solution precipitation metallic copper and blue copper sulphate solution turns green due to formation of ferrous sulphate.
Equation : CuSO₄ + Fe = FeSO₄ + Cu↓

Question 4.
In the burning of magnesium carbon-dioxide is not used as a fire ex­tinguisher why ?
Answer:
Explanation : Burning Magnesium produces heat which breaks carbon dioxide to carbon and oxygen. This oxygen enhance magnesium burning. SO₂, CO₂ is not used to extinguish magnesium burning.
Equation : Mg + CO₂ = MgO + C

Question 5.
Rain damages lajmahal. Do you agree ? Give reason.
Answer:
Reason : Rain water contains nitric acid. The nitric acid is formed by natural ways in the following manner. Nitrogen reacts with oxygen, both present in v air, by thunder to form nitric oxide. Nitric oxide further reacts with oxygen to form nitrogen dioxide.

Nitrogen dioxide dissolves in rain water to produce nitric acid. Tajmahal is made of lime stone i.e. Calcium carbonate (CaCO₃). Nitric acid (HNO₃) reacts with CaCO₃ to form Ca(NO₃)₂. Thus rain damages Tajmahal.
Equation : CaCO₃ + 2HNO₃ = Ca(NO₃)₂ + CO₂+ H₂O

Question 6.
What is Thermite ? What is its use ?
Answer:
Thermite : Thermite is a mixture of aluminium powder and ferric oxide.
Use : It is used for welding purposes.

Question 7.
State what happens when :
Zn is added to caustic soda solution
Answer:
Explanation : Zinc reacting with caustic soda solution produces sodium zincate and hydrogen gas.
Equation : Zn + 2NaOH = Na₂ZnO₂ + H₂↑

Question 8.
State what happens when :
Steam is passed over red hot iron.
Answer:
Explanation : When steam is passed over red-hot iron (600°C – 800°C), hydrogen is set free and iron is oxidised to ferrosoferric oxide.
Equation : 3Fe + 4H₂O = Fe₃O₄ + 4H₂↑

Question 9.
State what happens when :
Steam is passed over red hot zinc.
Answer:
Explanation : When steam is passed over red hot zinc, zinc oxide and hydrogen gas form.
Equation : Zn + H₂O= ZnO + H₂↑

Question 10.
What compounds are formed when magnesium is burnt in air ?
Answer:
Explanation : Magnesium oxide (MgO) and magnesium nitride (Mg₃N₂) are formed when magnesium is burnt in air.
Equation :
(a) 2Mg + O₂ = 2MgO
(b) 3Mg + N₂ = Mg₃N₂

Question 11.
What is Galvanisation ? State one use of Zinc.
Answer:
Galvanisation : It is a process of coating an article with zinc. The purpose of galvanisation an article is to protect it from corrosion. Iron articles are galvanised to protect the articles from rusting.
Use of Zinc : Zinc is largely used to prepare zinc white, a paint.

Question 12.
‘All ores are minerals but all minerals are not ores’ — Explain.
Answer:
Explanation : Compounds of a metal which exist in combination with similar compounds of other metals are known as minerals. A metal may occur in many minerals. The particular mineral from which a metal may be conveniently and eco­nomically extracted is called the ore of the metal.

Question 13.
What is Stainless steel ? State one use of it.
Answer:
Stainless steel : It is an alloy which composes Iron (Fe) = 73%, Chro­mium (Cr) = 18% and Nickel (Ni) = 8% and Carbon (C)
Uses of stainless steel : It is broadly used to make instruments.

Question 14.
What is Philosopher’s wool ?
Answer:
Philosopher’s wool : Zinc oxide is called philosopher’s wool, zinc white or Chinese white. It is a white powder which becomes yellow on heating and again becomes white on cooling. It is used as a white fluorescent paint because it is not darkened by hydrogen sulphide.

Question 15.
What is an alloy? Name one alloy.
Answer:
Alloy : An alloy is a homogeneous mixture (or, sometimes a heterogeneous combination) of two or more metals, behaving as a single metal in most of its physical properties.
Example : Bronze (Cu : 90% ; Sn : 10%)

Question 16.
State the advantages of an alloy over pure metal.
Answer:
Advantages of an alloy over pure metals :

• Increase of hardness.
• Increase in resistance to corrosion.
• Increase in fusibility or decrease in melting point.
• Improvement of casting property.

Question 17.
Two metals A and B produce hydrogen when react with hot NaOH solution. A does not react with H₂SO₄ but B produces a salt and hy­drogen gas reacting with H₂SO₄ Identify A and B.
Answer:
Identification : The metal A is aluminium and the metal B is zinc both of which react with hot NaOH solution to produce hydrogen.

Aluminium does not react with H₂SO₄ but zinc reacts with H₂SO₄ to produce salt and hydrogen.
Equation : Zn + H₂SO₄ = ZnSO, + H₂↑

Question 18.
What is the difference between mineral and ore of a metal ?
Answer:
Difference between mineral and ore of a metal :

Mineral	Ore
Compounds of a metal which exist in combination with similar compounds of other metals are known as minerals A metal may occur in many minerals.	The particular mineral from which a metal may be conveniently and economically extracted is called the ore of the metal.

Question 19.
Why alumina (Al₂O₃)cannot be reduced by carbon ?
Answer:
Explanation At high temperature, Al₂O₃ reacts with carbon to form alu­minium carbide.
Equation : \(2 \mathrm{Al}_2 \mathrm{O}_3+9 \mathrm{C} \rightleftharpoons \mathrm{Al}_4 \mathrm{C}_3+6 \mathrm{CO}\)

Question 20.
Why aluminium cannot be obtained by the electrolysis of fused AlCl₃?
Answer:
Explanation Aluminium cannot be obtained by the electrolysis of fused AlCl₃ since it is covalent solid and sublimes at 453K.

Question 21.
Although less conducting than copper, aluminium is used for power transmission. Why ?
Answer:
Explanation : Aluminium being lighter and cheaper than copper is used for power transmission.

Question 22.
What is the role of cryolite (Na₃AlF₆) in the electro-chemical reduc­tion of Al₂O₃ during the preparation of aluminium ?
Answer:
Explanation : Cryolite (Na₃AlF₆) is added to alumina ;

• to decrease its melting point from 2273K to 1173K.
• to increase its electrical conductivity.

Question 23.
Why aluminium acts as a good reducing agent ?
Answer:
Explanation : Reducing character of a substance depends upon its affinity for oxygen. Aluminium due to its high affinity for oxygen is a good reducing agent. It reduces a large number of oxides of other metals. e.g. 2Al + Fe₂O = Al₂O₃ + 2fe + heat.

Question 24.
Give reasons for the following:
Although aluminium is above hydrogen in electrochemical series, it is stable in air and water.
Answer:
Explanation : Aluminium reacts readily with air and water and a thin layer of its oxide gets deposited on its surface. This oxide coating protects the underlying metal from further action.

Question 25.
Aluminium containers can be used to store cone. HNO₃
Answer:
Explanation : Aluminium on treatment formation of a protective coating of its oxide. Thus aluminium containers can be used to transport cone. HNO₃

Question 26.
Finely powdered aluminium on exposure to air becomes hazadous. Why
Answer:
Explanation : Aluminium due to its great affinity for oxygen forms Al₂O₃ and the reaction is highly exothermic. Finely divided aluminium powder due to its large surface area, reacts vigorously with air and is hazardous.

Question 27.
Explain the following :
Anode mud in copper refining contains silver and gold.
Answer:
Explanation Silver and gold being less electropositive than copper are not ionised under the applied voltage and get deposited in the anode mud.

Question 28.
Explain the following :
Copper metal is largely used to make electrical cables.
Answer:
Explanation : Copper mainly used in making electrical cables because it is a good conductor. Moreover, being a noble metal, it is not affected by the atmosphere.

Question 29.
In moist air, copper corrodes to produce a green layer on the surface. Explain.
Answer:
Explanation : In presence of moist air, a thin layer of green basic copper carbonate is formed on the surface of copper leading to its corrosion.

Question 30.
Copper salts are coloured where as Zinc salts are colourless. Why
Answer:
Reason Copper salts are coloured because of the presence of an unpaired electron in Cu²⁺. This electron absorbs radiations of orange colour from white light for excitation from one energy level to another with the same d-subs shell. Hence, transmitted light appears blue. On the other hand, zinc salts are white because of the absence of vacant orbitals to which the electrons can be excited.

Question 31.
Explain why lime stone is used in the manufacture of pig iron from haematite.
Answer:
Explanation On heatingTime stone decomposes to give CaO which then combines with silica to form slag. Equation :
(a) CaCO₂ \(\rightleftharpoons\) CaO + CO₂
(b) SiO₂ + CaO = CaSiO₃ (slag)

Question 32.
What is the difference between cast iron. wrought iron and steel?
Answer:
Explanation The three forms differ in the percentage of carbon. Cast iron contains (2 -4-5)% carbon, wrought iron contains about 0-25% carbon, while steel contains (0T-T5)% carbon.

Question 33.
What is amalgam? Give example!
Answer:
Amalgam : If one of the components of an alloy is mercury then this alloy.

Broad Answer Type Questions

Question 1.
State the following:
(i) Chief one
(ii) Important properties and equations
(iii) Uses of:
(a) Aluminium
(b) Copper
(c) Iron
(d) Magnesium
(e) Zinc.
Answer:
List of chief ore, propetites, uses of Al, Cu, Fe, Mg, Zn :

Question 2.
State some alloy. with their composition and use :
Answer:
Common alloys of Al, Mg, Zn

Well structured WBBSE Class 10 Physical Science MCQ Questions Chapter 4 Thermal Phenomena can serve as a valuable review tool before exams.

Thermal Phenomena Class 10 WBBSE MCQ Questions

Multiple choice questions (MCQ) :

Question 1
The Fahrenheit and kelvin scales of temperature will the same reading at
(A) -40
(B) 313
(C) 574.25
(D) 732.25
Answer:
(B) 5 ?

Question 2
At what temperature, volume of an ideal gas at 0°C becomes triple?
(A) 182°C
(B) 819°C
(C) 546°C
(D) 646°C
Answer:
(C) 546°C

Question 3.
The specific heat of ice at 0°C melting into at 0°C is:
(A) zero
(B) infinity
C) more than zero
(D) less than zero
Answer:
(B) infinity

Question 4.
Boiling water is changing into steam. The specific heat of boiling water is:
(A) Zero
(B) One
(C) infinity
(D) less than one
Answer:
(C) infinity

Question 5.
Which of the following has the highest specific heat?
(A) copper
(B) water
(C) hydrogen
(D) silver
Answer:
(C) hydrogen

Question 6.
One gram of ice at 0°C is added at 5 g of water to 10°C. Final temperature of the mixture is:
(A) -5°C
(B) 5°C
(C) 0°C
(D) none of these
Answer:
(A) -5°C

Question 7.
The specific heat of an ideal gas varies with temperature T as :
(A) T¹
(B) T²
(C) T^-1
(D) T⁰
Answer:
(D) T⁰

Question 8.
22 g CO₂ at 27°C is mixed with 16 g of oxygen at 37°C. The temperature of the mixture is :
(A) 32°C
(B) 27°C
(C) 37°C
(D) 30°C
Answer:
(A) 32°C

Question 9.
A ballon contains 500 m³ of He at 27°C and 1 atmospheric pressure. The volume of He at -3°C and 0.5 atmospheric pressure will be:
(A) 700 m³
(B) 900 m³
(C) 1000 m³
(D) 500 m³
Answer:
(B) 900 m³

Question 10.
The specific heat of a gas in a gas in an isothermal process is:
(A) infinite
(B) zero
(C) negative
(D) remains constant
Answer:
(A) infinite

Question 11.
100 g of ice is mixed with 100 g of water at 100°C. The final temperature of the mixture is:
(A) 10°C
(B) 20°C
(C) 40°C
(D) 30°C
Answer:
(A) 10°C

Question 12.
Heat given to a body which rises its temperature by 1°C is:
A water equivalent
(B) specific heat
(C) thermal capacity
(D) temperature gradient
Answer:
(C) thermal capacity

Question 13.
During the adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature.
The ratio \(\fracC_p}C_v}\) for gas is :
(A) \(\frac{4}3}\)
(B) 2
(C) \(\frac{5}3}\)
(D) \(\frac{3}2}\)
Answer:
(D)

Question 14.
A gaseous mixture consists of 16 g of Helium and 16 g Oxygen. The ratio \(\fracC_p}C_v}\) of the mixture is :
(A) 1.54
(B) 1.4
(C) 1.63
(D) 1.59
Answer:
(C) 1.63

Question 15
Two bars of copper having same length but unequal cross-section are heated to the same temperature. The change in length will be:
(A) equal in both bars
(B) more in thicker bar
(C) more in thinner bar
(D) cannot say
Answer:
(A) equal in both bars

Question 16
A body cools from 60°C to 50°C in 10 min. If room temperature be 25°C, temperature of the body at the end of next 10 min will be:
(A) 38.5°C
(B) 40°C
(C) 45°C
(D) 42.85°C
Answer:
(D) 42.85°C

Question 17
A body takes T minutes is cool from 62°C to 61°C when the surrounding temperature is 30°C. The time taken by the body to cool is 30°C. The time taken by the body to cool 46°C to 45°C is
(A) greater than T minute
(B) equal to T minute
(C) less than T minute
(D) equal to T/2
Answer:
(A) greater than T minute

Question 18
If the temperature of a block body is doubled, the wavelength at which the spectral radiancy has its maximum is :
(A) doubled
(B) halved
(C) quadrupled
(D) unchanged
Answer:
(B) halved

Question 19
A black body has maximum wavelength 1 m at 2000 K. Its corresponding wavelength at 3000 K will be :
(A) \(\frac{3}{2}\) λ m
(B) \(\frac{2}{3}\) λ m
(C) \(\frac{16}{81}\) λ m
(D) \(\frac{81}{16}\) λ m
Answer:
(B) \(\frac{2}{3}\) λ m

Question 20.
A body cools from 50°C to 40°C in 5 minutes. Its temperature comes down to 33.33°C in next 5 minutes. The temperature of surrounding is:
(A) 15°C
(B) 20°C
(C) 25°C
(D) 10°C
Answer:
(B) 20°C

Question 21
The rate of cooling at 600 K, if surrounding temperature is 300 K is R. The rate of cooling at 900 K is :
(A) \(\frac{16}{3}\) R
(B) 2 R
(C) 3 R
(D) \(\frac{2}{3}\) R
Answer:
(A) \(\frac{16}{3}\) R

Question 22
If I_m denotes the wavelength at which the radiative emission from a black body at a temperature TK is maximum, then
(A) λ_m ∝ T
(B) λ_m ∝ T^-1
(C) λ_m ∝ T²
(D) λ_m does not depend on T.
Answer:
(B) λ_m ∝ T^-1

Question 23
Two spheres made of same material have radii in the ratio 1 : 2. Both are at same temperature. Ratio of heat radiation energy emitted per second by them is:
(A) 1 : 2
(B) 1 : 4
(C) 1 : 8
(D) 1 : 16
Answer:
(B) 1 : 4

Question 24.
The coefficient of linear expansion of a solid is :
(A) 3 γ
(B) 2 γ
(C) γ
(D) γ / 3
Answer:
(D) γ / 3

Question 25.
A good insulator of heat is
(A) Copper
(B) Mercury
(C) trapped air
(D) Iron
Answer:
(C) tropped air

Question 26.
A bimetallic strip bends on heating due to :
(A) Uneven expansions
(B) Same expansion
(C) No expansions
(D) None of these
Answer:
(A) Uneven expansions

Question 27.
The coefficient of linear expansion of a solid depends on :
(A) unit of length
(B) scale of temperature
(C) density of the material
(D) None of these
Answer:
(B) scale of temperature

Question 28.
A bimetallic strip bends upon heating because of
(A) same expansion
(B) uneven expansion
(C) no expansion
(D) twisting
Answer:
(B) uneven expansion

Question 29.
If the value of coefficient of linear expansion is 1.5 × 10^-4 ° C^-1 then value of coefficient of superficial expansion is :
(A) 4.5 × 10^-4 °C^-1
(B) 3.0 × 10^-4 ° C^-1
(C) 6.0 × 10^-4 ° C^-1
(D) 7.5 × 10^-4 ° C^-1
Answer:
(B) 3.0 × 10^-4 ° C^-1

Question 30.
When a solid metallic sphere is heated, the largest percentage increase occurs in its.
(A) Diameter
(B) Surface area
(C) Volume
(D) Density
Answer:
(C) Volume

Question 31.
For a liquid, the coefficient of apparent expansion (δ_a) and coefficient of real expansion (γ) are related as :
(A) δ_a = γ_r
(B) γ_a > γ_ru
(C) γ_a < γ_r
(D) γ_a / γ_r = constant
Answer:
(C) γ_a < γ_r

Question 32.
Coefficient of linear expansion of the following metals are in the order
(A) aluminium < copper < iron
(B) copper < iron < aluminium
(C) copper < aluminium < iron
(D) aluminium > copper > iron
Answer:
(D) aluminium > copper > iron

Question 33.
The thermal conductivity of a rod is 2. what is its resistivity?
(A) 0.5
(B) 1
(C) 0.25
(D) 2
Answer:
(A) 0.5

Question 34.
Thermal conductivity of which of the following is the maximum?
(A) copper
(B) silver
(C) diamond
(D) platinum
Answer:
(C) diamond

Question 35.
The magnitude of thermal conductivity of the following substances are in the order.
(A) silver > aluminium > glass > wood
(B) aluminium > silver > glass > wood
(C) silver > aluminium > wood > glass
(D) aluminium > silver > wood > glass
Answer:
(A) silver > aluminium > glass > wood

Question 36.
A liquid which is a good conductor of heat is :
(A) kerosin
(B) mercury
(C) water
(D) turpentine
Answer:
(B) mercury

Question 37.
For an ideal heat insulator, value of K is :
(A) zero
(B) 1
(C) 100
(D) α
Answer:
(A) zero

Fill in the blanks :

1. Heat is a form of _________.
Answer:
energy.

2. Three different types of motions are translational motion, vibrational motion and ___________.
Answer:
Rotational motion.

3. SI unit of heat is __________.
Answer:
Joule.

4. 1 calorie = __________ Jule.
Answer:
4.18

5. Temperatures are measured with a __________.
Answer:
thermometer.

6. ______ is the upper fixed point in Fahrenheit scale.
Answer:
212° F

7. Three types of expansions in solids are, linear expansion, superficial expansion and __________.
Answer:
volume expansion.

8. Real expansion of the liquid = expansion of the vessel + __________.
Answer:
apparent expansion of the liquid.

9. γ_s = γ_n + ________.
Answer:
γ₈

10. The volume of water is minimum at ______.
Answer:
4°C

11. The density of water is maximum at ______.
Answer:
4°C.

12. From Charle’s Law, we find γ_p = ______ °C^-1.
Answer:
\(\frac{1}{273}\)

13. From pressure law, we find γ_y= ________ °C^-1.
Answer:
\(\frac{1}{273}\)

14. Specific heat of water in SI system is ________.
Answer:
4200 Jkg^-1 K^-1.

15. The unit of thermal conductivity in SI system is ________.
Answer:
Jm^-1 s^-1 K^-1.

16. The unit of thermal conductivity in CGS system is ________.
Answer:
cm² s^-1

17. Carbon dioxide is a ________ gas.
Answer:
green house.

18. The expansion of a substance on heating is called ________ expansion.
Answer:
thermal.

19. The coefficient of linear expansion of a solid does not depend on unit of ________.
Answer:
length.

20. Thermal resistivity is the _______ of thermal conductivity.
Answer:
reciprocal.

21. In charles’ law, a _______ mass of gas is taken.
Answer:
given.

22. A liquid good conductor of heat is ________.
Answer:
mercury.

23. In summer the pendulum clock becomes ________.
Answer:
slower

24. The unit of γ (i.e, coefficlent of cubical expansion) in S.I unit is ________.
Answer:
K^-1

25. Material of the rod remaining same, longer the rod, ________ will be the increase in length of the rod for same increase in temperature.
Answer:
more.

26. If the value of α is 24 × 10^-6 °C^-1, then its value in S.I. unit is ________.
Answer:
24 × 10^-6 K^-1

27. Unit of β (coefficient of superficial expansion) is ________.
Answer:
°C^-1 or K^-1

28. For a particular solid substance, magnitude of β has the value of α [symbols have their usual meaning].
Answer:
twice

29. For two rods of same length and same area of cross-section, if temperature is raised by same amount, iron rod will expand ______ compared to that of the aluminium rod.
Answer:
less

30. The reciprocal of thermal conductivity is known as ________.
Answer:
thermal resistivity.

31. The S.I unit of thermal conductivity is ________.
Answer:
jm^-1.k^-1.s^-1

32. Diamond has ________ value of K (i.e., coefficient of thermal conduction) than copper.
Answer:
higher

33. Brass is a ________ conductor of heat.
Answer:
good

34. In solids, heat passes from hotter region to colder region by ________ processes.
Answer:
conduction

State whether the following statement is True or False : VSA

1. In winter the pendulum clock becomes slower.
Answer:
False

2. β (i.e. coefficient of superficial expansion) is the characteristic of the material.
Answer:
True

3. For an ideal gas, (δ i.e., coefficient of cubical expansion) = 1 / 273
Answer:
True

4. α, β and δ are related as follows α : β : δ = 1 : 2 : 3
[Symbols have their usual meaning]
Answer:
True

5. Real expansion of the liquid = Apparent expansion of the liquid+volume expansion of the container.
Answer:
True

6. The seasonal changes in a pendulum clock are due to the expansion or contraction of solid substances.
Answer:
True

7. The S.I. unit of thermal conductivity is jm^-2 ks^-1
Answer:
False

8. Usually metals are good conductors of heat than gases and nonmetals.
Answer:
True

9. Diamond has low value of K (i.e. coefficient of thermal conduction)
Answer:
False

10. In solids, heat passes from hotter region to colder region by convection processes.
Answer:
False

11. A substance with a large thermal conductivity is a good conductor while the one with a small thermal conductivity is a poor heat conductor.
Answer:
True

Well structured WBBSE Class 10 Physical Science MCQ Questions Chapter 8.4 Inorganic Chemistry in the Laboratory and in Industry can serve as a valuable review tool before exams.

Inorganic Chemistry in the Laboratory and in Industry Class 10 WBBSE MCQ Questions

(a) Ammonia

Multiple Choice Questions :

Question 1.
Ammonia is : ……………
(A) acidic
(B) basic
(C) neutral
(D) amphoteric
Answer:
(B) basic

Question 2.
The reaction N₂ + 3H₂ = 2NH₃ is ……………
(A) exothermic
(B) endothermic
(C) neither of the two
(D) Both of the two
Answer:
(A) exothermic

Question 3.
Liquid ammonia is used in refrigerators because : ……………
(A) It has a high dipole moment
(B) It has a high heat of evaporation
(C) of its basicity
(D) of its stability
Answer:
(B) It has a high heat of evaporation

Question 4.
High heat of vaporization of ammonia is due to its : ……………
(A) basic nature
(B) polar nature
(C) hydrogen bonding
(D) high solubility
Answer:
(C) hydrogen bonding

Question 5.
In the Ostwald process for the manufacture of HNO₃
(A) air is blown into an electric arc
(B) ammonia is catalytically oxidized
(C) chile saltpetre is treated with cone. H₂SO₄
(D) NaNO₃ is treated with cone. H₂SO₃
Answer:
(B) ammonia is catalytically oxidized

Question 6.
Which of the following statements is correct for the manufacture of ammonia by Haber’s process ?
(A) Low temperature, high pressure, presence of catalyst.
(B) High temperature, high pressure and catalyst
(C) Low temperature and pressure
(D) High temperature and low pressure
Answer:
(A) Low temperature, high pressure, presence of catalyst

Question 7.
Ammonia water makes a good cleaning agent because it: ……………
(A) is weakly basic
(B) emulsifies grease
(C) leaves no residue when wiped out
(D) all are true
Answer:
(D) all are true

Question 8.
A mixture of ammonia and air at about 800°C in the presence of Pt gauze forms : ……………
(A) N₂O
(B) NO
(C) NH₂OH
(D) NO
Answer:
(B) N₂O₃

Question 9.
Ammonium ion in solution is detected by ……………
(A) Brown-ring test
(B) Molish’s test
(C) Nessler’s solution
(D) Fehling’s solution
Answer:
(C) Nessler’s solution

Question 10.
The substance used for drying ammonia gas in the laboratory ……………
(A) cone. H₂SO₄
(B) P₂O₂
(C) quick lime
(D) silica gel
Answer:
(C) quick lime

Question 11.
Non-combustible hydride is : ……………
(A) NH₃
(B) PH₃
(C) ASH₃
(D) SbH₃
Answer:
(A) NH₃

Question 12.
Which is most explosive ?
(A) NCl₃
(B) PCl₃
(C) ASCl₃
(D) All
Answer:
(A) NCl₃

Question 13.
Ammonia gas is prepared in the laboratory by the action of slaked lime on ……………
(A) NH₄Cl
(B) (NH₄)₂SO₄
(C) NH₄Cl + NaNO₃
(D) NH₄NO₃
Answer:
(A) NH₄Cl

Question 14.
With excess of Cl₂ ammonia gives
(A) NCl₃
(B) HCl
(C) NH₄Cl
(D) N₂O
Answer:
(A) NCl₃

Question 15.
How NH₃ is generally manufactured for fertilizers ?
(A) by reducing the by product HNO₃
(B) passing a mixture of N₂ and H₂ under high pressure and moderate temperature over a catalyst
(C) by passing an electric discharge in the mixture of H₂ and N₂
(D) 2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2NH₃ + 2H₂O
Answer:
(B) passing a mixture of N₂ and H₂ under high pressure and moderate temperature over a catalyst

Question 16.
Liquid NH₃ bottles are opened only after cooling for some time. This is because :
(A) NH₃ is corrosive liquid
(B) it is a mild explosive
(C) it brings tears in eyes
(D) it generates high vapour pressure.
Answer:
(D) it generates high vapour pressure

Question 17.
Aqueous solution of ammonia consists of :
(A) H⁺
(B) OH^–
(C) NH
(D) NH₄⁺+ OH^–
Answer:
(D) NH₄⁺+ OH^–

Question 18.
The vapour density of ammonia is:
(A) 7
(B) 7.5
(C) 8.5
(D) 17
Answer:
(C) 8.5

Question 19.
Nessler’s reagent is :
(A) K₂Hgl₄
(B) K₂Hgl₄ + KOH
(C) K₂Hgl₄
(D) K₂Hgl₄ + KOH
Answer:
(B) K₂Hgl₄ + KOH

Question 20.
Cupric hydroxide dissolves in aqueous ammonia due to
(A) reduction to cuprous hydroxide
(B) complex formation
(C) increase in pH
(D) the amphoteric nature of Cu(OH)₂
Answer:
(B) complex formation

Question 21.
The blue complex formed on addition of cone. NH₄OH solution to a Cu2+ salt solution has the structure :
(A) \(\left[\mathrm{Cu}\left(\mathrm{NH}_4\right)_4\right]^{2+}\)
(B) \(\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_2\right]^{2+}\)
(C) \(\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+}\)
(D) \(\left[\mathrm{Cu}\left(\mathrm{NH}_4\right)_2\right]^{2+}\)
Answer:
(C) \(\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_4\right]^{2+}\)

Question 22.
On addition of NH₄OH to a copper sulphate solution :
(A) blue precipitate of copper hydroxide is obtained
(B) black precipitate of copper oxide is obtained
(C) a deep blue solution is obtained
(D) no change is observed
Answer:
(C) a deep blue solution is obtained

Question 23.
In which the ammonia is not used ?
(A) Cold storage
(B) Anaesthetic
(C) Manufacture of rayon and plastic
(D) None of these.
Answer:
(B) Anaesthetic

Question 24.
In the reaction : \(\mathbf{N}_2+3 \mathrm{H}_2 \rightleftharpoons 2 \mathrm{NH}_3,\) the catalyst used is :
(A) Pt and Cu
(B) Fe and Mo
(C) NO + Pt
(D) Ni + Ti
Answer:
(B) Fe and Mo

Question 25.
Ammonia can be obtained by heating ammonium sulphate with :
(A) KOH
(B) NaCl
(C) CaCl₂
(D) ZnSO₄
Answer:
(A) KOH

Question 26.
Ammonia is collected by :
(A) downward displacement of water
(B) downward displacement of air
(C) upward displacement of air
(D) by downward displacement of hot water
Answer:
(B) downward displacement of air

Question 27.
Ammonia is :
(A) basic
(B) acidic
(C) neutral
(D) insoluble in water
Answer:
(A) basic

Question 28.
Ammonium chloride and Ca(OH)₂ on heating produce :
(A) N₂
(B) NO₂
(C) NH₃
(D) NO
Answer:
(C) NH₃

Question 29.
Liquid ammonia contains :
(A) 35% NH₃
(B) 60% NH₃
(C) 80% NH₃
(D) 0.0% NH₃
Answer:
(A) 35%NH₃

Fill in the blanks

1. Ammonia gas is prepared by heating on ammonium salt mixed with a strong ……………………..
Answer:
base

2. Ammonia produces a white cloud with ……………………. acid.
Answer:
hydrochloric

3. Ammonia turns red litmus solution ……………………..
Answer:
blue

4. Ammonia has a typical ……………………. smell.
Answer:
pungent

5. Aqueous solution of ammonia is …………………….
Answer:
alkaline

6. A ……………. aqueous solution of ammonia is called liquor ammonia.
Answer:
Concentrated

7. Ammonia gas when passed over heated sodium, amide salt and ……………. gas produce.
Answer:
hydrogen

8. Since ammonia gas is …………….than air, it is collected by downward displacement of air.
Answer:
lighter

9. Ammonia is dried by passing through …………….
Answer:
quick lime

10. Ammonia is ………………. soluble in water.
Answer:
highly

11. In ammonia we have nitrogen and ……………..
Answer:
hydrogen

12. Ammonia gas is passed over heated black cupric oxide which is reduced to red metallic …………….
Answer:
copper

13. 2NH₃Cl + Ca(OH)₂ = _________ + CaCl₂ + 2H₂O
Answer:
2NH₃

14. When excess chlorine reacts ammonia forming nascent nitrogen which again combines with chlorine producing, ………… an oily yellow explosive compound.
Answer:
nitrogen trichloride.

15. ………… gas is obtained by heating ammonium sulphate with sodium hydroxide.
Answer:
Ammonia

16. ………… reagent is used for the identification of ammonia.
Answer:
Nessler’s

17. Ammonia is ………… for eyes.
Answer:
harmful

18. Ammonia gas is collected by the ………… displacement of air.
Answer:
downward.

19. Ammonia is dried with …………
Answer:
calcium oxide.

20. When ammonia leaks from factory we should wash our eyes with …………….
Answer:
water.

21. is an inorganic fertilizer which is produced from ammonia.
Answer:
Ammonium sulphate [(NH₄)₂SO₄]

22. is an organic fertilizer which is produced from ammonia.
Answer:
Urea [CO(NH₂)₂]

23. HNO₃ ………… is manufactured from ammonia by process.
Answer:
Ostwald.

(b) Sulphuretted Hydrogen (H₂S)

Multiple Choice Questions :

Question 1.
Which of the following oxidation states is applicable to sulphur in H₂S?
(A) -2
(B) +5
(C) +6
(D) +3
Answer:
(A) -2

Question 2.
An example of non-linear molecule is :
(A) H₂S
(B) CO₂
(C) C₂H₂
(D) N₂O
Answer:
(A) H₂S

Question 3.
H₂S on Incomplete combustion forms mainly
(A) HO and S
(B) H and SO₂
(C) H₂S and S
(D) H₂O and SO₂
Answer:
(C) H₂S and S

Question 4.
H₂S is a: ……….
(A) weak dibasic acid
(B) strong dibasic acid
(C) weak monobasic acid
(D) monobasic
Answer:
(C) Weak dibasic acid

Question 5.
When QuestionH₂S is passed through acidified KMnO₄
(A) KHSO₂
(B) K₂SO₄
(C) MnO₂
(D) S
Answer:
(D) S

Question 6.
Which of the following turns lead acetate paper black?
(A) SO₂
(B) SO₃
(C) H₂S
(D) H₂SO₄
Answer:
(C) H₂S

Question 7.
Sulphuretted hydrogen was discovered by:
(A) Shele
(B) Dalton
(C) Lavoisier
(D) Richter
Answer:
(A) Shele

Question 8.
H₂S is :
(A) alkaline
(B) neutral
(C) acidic
(D) amphoteric gas
Answer:
(C) acidic

Question 9.
When a strip of filter paper, soaked in colourless lead acetate solution, is held in the H₂S gas the filter paper becomes
(A) black
(B) blue
(C) pink
(D) red
Answer:
(A) black

Question 10.
Molecular weight of H₂S is:
(A) 32
(B) 34
(C) 36
(D) 38
Answer:
(A) 34

Question 11.
FeS reacts with
(A) dil. H₂SO₄
(B) Conc. H₂SO₄
(C) Conc.HNO₃ to form H₂S
(D) None of these
Answer:
(A) dil. H₂SO₄

Question 12.
H₂S is passed through a added to it. The solution
(A) violet
(B) black
(C) green
(D) red
Answer:
(A) violet

Question 13.
H₂S gas has a smell:
(A) like roften eggs
(B) pungent
G smell like fish none of these
Answer:
(C) smell like fish

Question 14.
H₂S is: ……………
(A) heavier
(B) lighter
(C) slightly heavier than air
(D) none of these
Answer:
(C) smell like fish

Question 15.
Aqueous soution of the gas turns blue litmus to red:
(A) H₂S
(B) NH₃
(C) O₂
(D) H₂
Answer:
(A) H₂S

Question 16.
H₂S can be collected in downward displacement of
(A) hot water
(B) cold water
(C) Hg
(D) none of these
Answer:
(A) hot water

Question 17.
mejas which is identified by its smell:
(A) Nitrogen
(B) Hydrogen
(C) Hydrogen sulphide
(D) None of these
Answer:
(C) Hydrogen sulphide

Question 18.
The gas which has reducing property:
(A) H₂S
(B) CO₂
(C) NO₂
(D) none of these
Answer:
(A) H₂S

Question 19.
H₂S gas is passed through :
(A) P₂O₅
(B) Anhydrous CaCl₂
(C) CaO
(D) none of these
Answer:
(A) P₂O₅

Question 20.
The gas which is absorbed by NaOH :
(A) NH₃
(B) H₂S
(C) O₂
(D) None of these
Answer:
(B) H₂S

Fill in the Blanks:

1. H₂S is a gas having the smell of ……………………
Answer:
rotten egg

2. H₂S is a good ………….. agent.
Answer:
reducing

3. Hydrogen sulphide is a combustible gas but not a supporter of ……………..
Answer:
combustion

4. H₂S reduces acidified yellow solution of ferric chloride to colourless chloride.
Answer:
ferrous

5. Aqueous solution of H₂S is a mild acid, it turns blue ……………. red.
Answer:
litmus

6. H₂S gas has the characteristic unpleasant smell of rotten
Answer:
egg

7. H₂S + H₂SO₄ (cone.) = S + ……………. + 2H₂O
Answer:
SO₂

8. Pb(CH₂COO)₂ + H₂S = ……………….. +2 CH₂COOH
Answer:
PbS

9. H₂S gas turns lead acetate ……………..
Answer:
black

10. H₂S gas is 1.5 times heavier than ……………..
Answer:
air

11. Dilute H₂SO₄ is preferred to dilute HCl acid, for the latter is very ……………..
Answer:
volatile

12. Presence of ………………… gas in the atmosphere in traces tarnishes silver to black silver sulphide.
Answer:
H₂S

13. On passing H₂S gas through zinc salt solution in ………………… medium sulphide of zinc gets precipitated.
Answer:
basic

14. Hydrogen sulphide reduces concentrated sulphuric acid to …………………
Answer:
SO₂

15. Hydrogen sulphide reduces concentrated nitric acid to …………………
Answer:
NO₂

16. Molecular formula of sulphuretted hydrogen is …………………
Answer:
H₂S

17. ………………… is used in order to dry H₂S.
Answer:
P₂O₅

18. H₂S is appreciable soluble in ………………… water, but practically insoluble in not water.
Answer:
cold                                                                                                                     .

19. H₂S is a weak ………………… acid.
Answer:
dibasic

(c) Nitrogen

Multiple choice questions (MCQ) :

Question 1.
The boiling point of liquid nitrogen is
(A) 0°C
(B) – 195.7°C
(C) – 180°C
(D) – 273°C
Answer:
(B) – 195.7°C

Question 2.
Chlorine present as impurity in nitrogen gas is removed by :
(A) Conc. NaOH
(b) Conc. H₂SO₄
(C) P₂O₅
(D) KNO₃
Answer:
(A) Conc. NaOH

Question 3.
The formula of an Inorganic fertilizer containing nitrogen is :
(A) NH₄Cl
(B) (NH₄)₂SO₄
(C) HCN
(D) Pb(NO₃)₂
Answer:
(B) (NH₄)₂SO₄

Question 4.
How is nitrogen gas dried :
(A) Passing through conc.H₂SO₄
(B) By heating the gas in a vessel
(C) P₂O₅
(D) CaCl₄
Answer:
(A) Passing through conc.H₂SO₄

Question 5.
What is the product of combination of nitrogen with calcium carbidc?
(A) calcium nitride
(B) calcium nitrate
(C) calcium nitrite
(D) calcium cyanamide
Answer:
(D) calcium cyanamide

Question 6.
How does nitrogen combine with oxygen :
(A) The two gases combine at a very high temperature under electric spark
(B) The two gases directly combine in presence of sunlight
(C) In absence of sunlight
(D) In presence of iron catalyst.
Answer:
(A) The two gases combine at a very high temperature under electric spark

Question 6.
How does nitrogen combine with oxygen :
(A) The two gases combine at a very high temperature under electric spark
(B) The two gases directly combine in presence of sunlight
(C) In absence of sunlight
(D) In presence of iron catalyst.
Answer:
(A) The two gases combine at a very high temperature under electric spark

Question 7.
What is the necessity of presence of ñttrogen in air:
(A) Nitrogen helps respiration of plants
(B) Nitrogen helps respiration of animals
(C) Nitrogen helps to burn
(D) Nitrogen helps to control burning in air.
Answer:
(D) Nitrogen helps to control burning in air

Question 8.
Why is not nitrogen gas prepared by heating NH₄NO₂ directly :
(A) Rapid explosive dissociation takes place
(B) Nitrogen gas is not obtained
(c) Nitrogen gas combines with oxygen in air
(D) None of these.
Answer:
(A) Rapid explosive dissociation takes place

Question 9.
At ordinary temperature nitrogen is ________
(A) reactive
(B) inert
(C) very-active
(D) None of these.
Answer:
(B) inert

Question 10.
The solubility of nitrogen in water is :_______
(A) low
(B) very low
(C) high
(D) very high
Answer:
(B) very low

Question 11.
Nitrogen is ______
(A) heavier
(B) lighter
(C) slightly heavier
(D) slightly lighter than air
Answer:
(D) slightly lighter

Question 12.
The conversion of Nitrogen gas to liquid nitrogen is :_____________
(A) possible
(B) impossible
(C) easily possible
(D) possible but difficult
Answer:
(D) possible but difficult

Question 13.
Which of the following compounds is used as fertilizer ?
(A) calcium carbide
(B) calcium chloride
(C) magnesium nitride
(D) nitrolim
Answer:
(D) nitrolim

Question 14.
Who discovered nitrogen_______
(A) Daniel Rutherford
(B) Bohr
(C) Dalton
(D) Lavoisier
Answer:
(A) Daniel Rutherford

Question 15.
Nitrogen containing organic fertilizer is :________
(A) nitrolim
(B) ammonium sulphate
(C) ammonium nitrate
(D) urea
Answer:
(D) urea

Question 16.
The requisite chemicals for the preparation of nitrogen :___________
(A) NH₄Cl and Ca(OH)₂
(B) NaNO₂ and NH₄Cl
(C) (NH₄)₂SO₄ and NaOH
(D) NH₄CL and NaOH
Answer:
(B) NaNO₂ and NH₄Cl

Question 17.
Nitrogen gas is collected by :___________
(A) downward displacement of water
(B) downward displacement of air
(C) upward displacement of air
(D) None of these
Answer:
(A) downward displacement of water

Question 18.
Percentage of nitrogen in air by volume is :_______
(A) 20
(B) 30
(C) 78
(D) 88
Answer:
(C) 78

Fill in the blanks

1. Solubility of nitrogen in water is very___________
Answer:
low

2. Nitrogen is a_________ gas._____________
Answer:
colourless

3. Liquid nitrogen is used as ________
Answer:
Condenser

4. 3Mg + N₂ =…………………
Answer:
Mg₃N₂

5. N₂ + ________  = 2NH₃
Answer:
3H₂

6. CaC₂ + N₂ = ________  + C
Answer:
CaCN₂

7. _______ has main role in protein synthesis.
Answer:
Nitrogen

8. The density of nitrogen gas is _____ g/L at NTP.
Answer:
1-25

9. Nitrogen is slightly _______  than air.
Answer:
lighter

10. Solubility of nitrogen in water is about ________  ml/L at NTP.
Answer:
23.5

11. With the help of electric spark nitrogen combines with oxygen at about 3000°C to produce ………..
Answer:
nitric oxide.

12. Nitrolim reacts with steam to form calcium carbonate and__________
Answer:
ammonia.

13. Ammonium nitrite decomposes into nitrogen and __________  due to heating.
Answer:
water

14. Nitrogen gas is passed over concentrated_______ acid where by dry nitrogen is obtained.
Answer:
sulphuric

15. Nitrogen gas is collected by the _________  displacement of water.
Answer:
downward.

16. Nitrogen is relatively_________ element
Answer:
non-reactive

17. Natural source of nitrogen is  _______
Answer:
air

18. The requisite chemicals used for the preparation of nitrogen are sodium nitrite and ______
Answer:
ammonium chloride.

19. Nitrogen was discovered by ________  in 1772.
Answer:
Daniel Rutherford

20. Nitrogen combines with oxygen forming nitric oxide under the influence of electric arc at a temperature of _________
Answer:
3000°C…….

21. Nitrogen combines with hydrogen in presence of electric sparks to produce ________
Answer:
Ammonia

22. When calcium carbide is heated in a current of nitrogen at temperature of ………….. calcium cyanamide and carbon are formed.
Answer:
1100°C

(d) Hydrogen Chloride (Hydrochloric acid), Nitric acid and Sulphuric acid

Multiple choice questions (MCQ) :

Question 1.
How does copper react with sulphuric acid ?
(A) Copper reacts with sulphuric acid in all forms
(B) Copper reacts with hot and concentrated sulphuric acid
(C) Copper reacts with dilute sulphuric acid
(D) None of these
Answer:
(B) copper reacts with hot and concentrated sulphuric acid.

Question 2.
What is passive iron and how it produces ?
(A) Chemically inactive iron is passive iron. It produces as insoluble coating of Fe₃O₄ forms on iron in contact with nitric acid
(B) Iron is inactive with all acids, so iron is passive
(C) It forms Fe₂O₃
(D) None of these
Answer:
(A) Chemically inactive iron is passive iron. It produces as insoluble coating of Fe₃O₄ forms on iron in contact with nitric acid.

Question 3.
In contact process for the production of H₂SO₄ on an industrial scale, the impurities of arsenic are removed by :
(A) Fe₂O₃
(B) Al(OH)₃
(C) Fe(OH))₃
(D) Cr(OH)₃
Answer:
(C) Fe(OH)₃

Question 4.
The conversion of SO₂ by O₂ into SO₃ is :_____
(A) an irreversible reaction
(B) an endothermic reaction
(C) an exothermic reaction
(D) none of these
Answer:
(C) An exothermic reaction

Question 5.
The most favourable condition for the conversion of
\(2 \mathrm{SO}_2+\mathrm{O}_2 \rightleftharpoons 2 \mathrm{SO}_3+98\) KJ/mole is:_____
(A) low temperature and high presure
(B) high temperature and low pressure
(C) high temperature and high pressure
(D) low temperature and low pressure
Answer:
(A) Low temperature and high pressure

Question 6.
In the contact process, sulphur trioxide is dissolved in :
(A) water
(B) dilute sulphuric acid
(C) cone sulphuric acid
(D) none of these
Answer:
(C) Cone., sulphuric acid

Question 7.
Which of the following statements concerning the manufacture of sulphuric acid is false ?
(A) Sulphur is burnt in air to produce SO₂
(B) SO₂ is catalytically oxidised to SO₃
(C) SO₃ is dissolved in water to get 100% sulphuric acid
(D) The lead chamber process for its manufacture is not much in use these days.
Answer:
(C) SO₃ is dissolved in water to get 100% sulphuric acid

Question 8.
Contact process is superior to chamber process for the manufacture of sulphuric acid as it:
(A) provides acid of any concentration
(B) gives acid of low concentration
(C) provides impure acid
(D) Occupies large space
Answer:
(A) provides acid of any concentration

Question 9.
Oleum is :
(A) H₂SO₅
(B) H₂S₂O₇
(C) H₂S₂O₈
(D) H₂SO₃
Answer:
(B) H₂S₂O₇

Question 10.
Oil of vitriol is :
(A) H₂SO₃
(B) H₂SO₄
(C) H₂S₂O₇
(D) H₂S₂O₈
Answer:
(B) H₂SO₄

Question 11.
Which is not correct in case of H₂SO₄ ?
(A) Oxidising agent
(B) Reducing agent
(C) Sulphonating agent
(D) Dehydrating agent
Answer:
(B) Reducing agent

Question 12.
Cone. H₂SO₄ is not :
(A) hygroscopic
(B) dehydrating agent
(C) sulphonating agent
(D) efflorescent
Answer:
(D) efflorescent

Question 13.
Catalyst used In the manufacture of H₂SO₄ by lead chamber process is: _________
(A) V₂O₅
(B) Pt
(C) Ni
(D) oxides of nitrogen
Answer:
(D) oxides of nitrogen

Question 14.
When sugar is treated with cone. H₂SO₄ the sugar becomes black due to;
(A) dehydration
(B) hydration
(C) hydrolysis
(D) decolourisation
Answer:
(D) decolourisation

Question 15.
Electrolysis of…. pure H₂SO₄ produces at anode :
(A) H₂S₂O₅
(B) H₂S₄O₆
(C) H₂S₂O₈
(D) H₂
Answer:
(C) H₂S₂O_s

Question 16.
When charcoal is heated with cone H₂SO₄ 
(A) there is no reaction
(B) CO₂ and SO₂ are evolved
(C) water gas is formed
(D) CO₂ and SO₂ are not evolved
Answer:
(B) CO₂ and SO₂ are evolved

Question 17.
Fuming sulphuric acid is commercially known as: ______
(A) Carro’s acid
(B) Marshall’s acid
(C) Oleum
(D) Sulphurous acid.
Answer:
(C) Oleu

Question 18.
Which of the following gives carbon with cone. H₂SO₄?
(A) Ethyl alcohol
(B) Starch
(C) Formic acid
(D) Oxalic acid
Answer:
(C) Formic acid

Question 19.
King of chemicals is
(A) H₂SO₄
(B) Oxalic acid
(C) HNO₃
(D) NaOH
Answer:
(A) H₂SO₄

Question 20.
Sulphuric acid is a dibasic in nature, hence it forms :
(A) acidic salt
(B) acidic and basic salt
(C) acidic and normal salt
(D) double salt.
Answer:
(C) acidic and normal salt

Question 21.
The main difference between nitric acid and hydrochloric acid lies in their reaction of
(A) nitrates
(B) chlorides
(C) metals
(D) bicarbonates
Answer:
(C) metals

Question 22.
The most volatile compound among the following is :
(A) HF
(B) HCl
(c) HBr
(d) Hl
Answer:
(B) HCl

Question 23.
Cone. HNO₃ oxidises phosphorus to: …………..
(A) H₃PO₄
(B) P₂O₅
(C) H₂PO₃
(D) H₄P₂O₇
Answer:
(A) H₃PO₄

Question 24.
When concentrated HNO₃ is heated, it decomposes to give :
(A) O₂ and N₂
(B) NO
(C) O
(D) NO₂ and O₂
Answer:
(D) NO₂ and O₂

Question 25.
Aqua fortis is :
(A) HNO₃
(B) HNO₂
(C) H₂NO₃
(D) H₂N₂O₂
Answer:
(A) HNO₃

Question 26.
The process used to manufacture nitric acid is :
(A) Solvay process
(B) Ostwald process
(C) Hall process
(D) Haber process
Answer:
(B) Ostwald process

Question 27.
‘Sulphan’ is …………..
(A) 20% oleum
(B) 80% oleum
(C) 100% oleum
(D) 88% oleum
Answer:
(C) 100% oleum

Question 28.
Specific gravity of liquor ammonia is :________
(A) 0.80
(B) 0.44
(C) 0.88
(D) 0.66
Answer:
(C) 0.88

Question 29.
In Haber’s process, the product is :_____
(A) CO(NH₂)₂
(B) NH₃
(C) HNO₃
(D) H₂SO₄
Answer:
(B) NH₃

Question 30.
Which of the following responds in nitroprusside test?
(A) HCl
(B) NH₃
(C) N₂
(D) H₂S
Answer:
(D) H₂S

Question 31.
The optimum temperature for industrial preparation of H₂SO₄ is :___
(A) 650°c
(B) 850°c
(C) 450°c
(D) 250°c
Answer:
(C) 450°c

Question 32.
Raw material for manufacture of HCl by Le Blanck process is :_____
(A) NaCl
(B) Na₂SO₄
(C) NH₄Cl
(D) CaCl₂
Answer:
(A) NaCl

Question 33.
Which of the following gases can be prepared by kipp’s apparatus?
(A) N₂
(B) H₂S
(C) HCl
(D) NH₃
Answer:
(B) H₂S

Question 34.
Choose the wrong statement :
(A) H₂S is a yellow cofoured gas
(B) H₂S is heavier than air
(C) H₂S has rotten egg like smell
(D) The aqueous solution of H₂S is acidic
Answer:
(A) H₂S is a yellow coloured gas

Question 35.
Choose the wrong statement :
(A) Ammonia is a colourless gas
(B) Ammonia is heavier than air
(C) Ammonia is highly soluble in water
(D) Ammonia can be easily liquefied by applying pressure.
Answer:
(B) Ammonia is heavier than air

Question 36.
Which one of the following is not a fertilizer?
(A) ammonia
(B) ammonium phosphate
(C) ammonium nitrate
(D) ammonium sulphate
Answer:
(A) ammonia

Fill in the blanks

1. In contact process, during the preparation of SO₃ from SO₂__________ is used as catalyst.
Answer:
V₂O₅

2. H₂S gas is __________ than air.
Answer:
heavier

3. An aqueous solution of H₂S litmus red.
Answer:
blue

4. In ostwald’s process, for the preparation of nitric acid _______ is used as catalyst.
Answer:
platinum

5. Red hot magnesium reacts with nitrogen to form
Answer:
Mg₃N₂

6. Ammonia gas prepared in the laboratory is dried by__________
Answer:
CaO

7. Ammonia has a strong …………..smell.
Answer:
pungent

8. In the laboratory, H₂S is prepared by the action of dilute H₂SO₄ acid on________
Answer:
FeS

9. Calcium Cyanamide is prepared by reaction between cac₂ and______at elevated temperature.
Answer:
N₂

10. Urea is prepared by reaction between NO₃ and________ at elevated temperature and high pressure.
Answer:
CO₂

State whether the following statement is True or False :

1. Nitrogen is slightly heavier than air.
Answer:
False

2. HCl is produced as a by-product during the manufacture of sodium sulphate by ostwald’s process.
Answer:
False

3. H₂S is a poisonous gas.
Answer:
True

4. In presence of air, H₂S burns with blue flame.
Answer:
True

5. Ammonia is used for production of fertilizers like urea.
Answer:
True

6. Ammonia is prepared by heating a dry ammonium salt with a dry alkali.
Answer:
True

7. P₂O₅ is acidic so it reacts with ammonia.
Answer:
True

8. Ammonia is highly soluble in water.
Answer:
True

9. H₂S is a strong oxidizing agent.
Answer:
False

10. In presence of air, H₂S burns with blue flame.
Answer:
True

Detailed explanations in West Bengal Board Class 10 Physical Science Book Solutions Chapter 8.3 Electricity and Chemical Reactions offer valuable context and analysis.

WBBSE Class 10 Physical Science Chapter 8.3 Questionuestion Answer – Electricity and Chemical Reactions

Very Short Answer Type Questions

Question 1.
Which agent conducts electricity through an electrolyte ?
Answer:
Ions conduct electricity through an electrolyte.

Question 2.
What is a Voltameter ?
Answer:
Voltameter is a vessel in which electrolysis is carried out.

Question 3.
What is function of acid or alkali mixed in water during electrolysis of water ?
Answer:
Acid or alkali increases number of ions that help electrolysis.

Question 4.
Name two electrolytes
Answer:
Aqueous solution of sulphuric acid (H₂SO₄), aqueous solution of sodium chloride (NaCl)

Question 5.
Name two non-electrolytes.
Answer:
Sugar solution, glycerine are two non-electrolytes.

Question 6.
What type of particles flow during electrolysis ?
Answer:
Positive and negative ions flow during electrolysis.

Question 7.
What are the electrodes used in the extraction of aluminium ?
Answer:
The carbon-lined iron tank is made the cathode and the anode is a set of carbon rods used in extraction of aluminium.

Question 8.
What is an ion ?
Answer:
Ion is an atom or radical carrying electric charge.

Question 9.
What is ionic dissociation ?
Answer:
The decomposition process of electrolytes into ions is known as ionic dis­sociation.

Question 10.
How does an atom convert to ion ?
Answer:
An atom converts to an ion either by losing or by gaining electron.

Question 11.
Which is more stable atom or ion ?
Answer:
Ion is more stable than atom.

Question 12.
What is the function of electric current in electrolysis ?
Ans.
The electric current sent into an electrolyte from a battery or any other external source only separates the two types of ions, it does not ionize the electrolyte.

Question 13.
In which state an electrolytic substance should exist during electrolysis ?
Answer:
During electrolysis an electrolytic substance should be fused state or in the state of aqueous solution.

Question 14.
What is cathode ?
Answer:
The electrode connected to the negative terminal of battery is called cathode.

Question 15.
What is anode ?
Answer:
The electrode connected to the positive terminal of battery is called anode.

Question 16.
What are cations ?
Answer:
The positive ions that move to the cathode are known as cations.

Question 17.
What are anions ?
Answer:
The negative ions that move to the anode are known as anions.

Question 18.
Which one is electrolyte ? – gold, mercury, common salt.
Answer:
Common salt is an electrolyte.

Question 19.
A brass spoon is to be nickel plated. Which is to be used as anode and which is to used as cathode ?
Answer:
Anode : Pure metal plate or rod of nickel.
Cathode : The brass spoon.

Question 20.
Name a substance which is a good conductor but not an electrolyte.
Answer:
Graphite is a good conductor but not an electrolyte.

Question 21.
Name a metal and a non-metal which can be used as electrodes.
Answer:
Metal : Platinum.
Non-metal : Graphite.

Question 22.
Is mercury an electrolyte ?
Answer:
Mercury is a good conductor but not electrolyte.

Question 23.
What is the meaning of ‘ion’ ?
Answer:
Ion’ has been derived from a Greek word meaning ‘wanderer’ or ‘traveller’ because the ions in a solution move about constantly in a random manner.

Question 24.
Between H^A and Ag^A which one will be discharged first at cathode ?
Answer:
Between H^⊕ and Ag^⊕, Ag^⊕ will be discharged first at cathode as the position of Ag^⊕ is below the position of H^⊕  in electro chemical series.

Question 25.
What is the nature of mercury ?
Answer:
Mercury is good conductor of electricity.

Question 26.
In electrolysis which energy is converted into which energy ?
Answer:
In electrolysis, electrical energy is converted into chemical energy.

Question 27.
Between Br^– and OH^– which ion will be discharged first at anode ?
Answer:
Between Br^– and OH^–, OH^– ion will be discharged first at anode as the position of OH^– ion is lower than that of Br in electrochemical series.

Question 28.
State one strong electrolyte.
Answer:
Strong electrolyte is H₂SO₄.

Question29.
Name one weak electrolyte.
Answer:
Acetic acid is an example of weak electrolyte.

Question 30.
What is called fluorspar ?
Answer:
CaF₂ is called flurospar.

Question 31.
What is called cryolite ?
Answer:
AlF₃, 3NaF is called cryolite.

Question 32.
In electrolysis of acidified water dilute sulphuric acid is preferred to dilute nitric acid or acidification. Explain.
Answer:
Both the acids may be used for acidification but dilute nitric acid is volatile and hence, less preferred compared to dilute sulphuric acid.

Question 33.
Write two applications of electrolysis in which the anode diminishes in mass.
Answer:
Electroplating of an article and electrorefining of metals.

Question 34.
Name a liquid which is non-electrolyte.
Answer:
Ethyl alcohol

Question 35.
What kind of particles will be found in a liquid compound which is a non-electrolyte?
Answer:
molecules.

Question 36.
Which one among OH^Θ or Na^⊕ will be discharged at anode?
Answer:
Anions are discharged at anode. Hence OH^Θ will be discharged at anode.

Question 37.
Name a liquid which conducts electricity but is not an electrolyte.
Answer:
Liquid metal mercury (Hg).

Question 38.
What do you mean by electrometallurgy?
Answer:
Electrometallurgy is the process of extraction of metals (which are at the top of electro chemical series) by electrolysis.

Question 39.
Name two metals other than aluminium which are extracted by electrolysis.
Answer:
Sodium (Na) and Magnesium (Mg) are extracted by the electrolysis of their molten chlorides with iron as cathode and graphite as anode.

Question 40.
What is used as anode and cathode during electrorefining of copper?
Answer:
Thin strip (or plate or wires) of pure copper is used as cathode and impure copper is used as anode during electrorefining of copper.

Question 41.
In case of electroplating of silver what is used as the electrolyte?
Answer:
Potassium argentocyanide K(Ag(CN)₂] is used as the electrolyte in case of electroplating of gold.

Short Answer Type Questions     

Question 1.
What is called Electrochemistry ?
Answer:
Electrochemistry : It is the branch of chemistry which deals with the relationship between chemical energy and electrical energy and how one can be converted into another.

Question 2.
What are Electrochemical reactions ?
Answer:
Electrochemical reactions : Oxidation and reduction-the loss and gain of electrons occur in many chemical reactions. When these reactions can be made to cause electrons to flow through a wire or when a flow of electrons makes a redox reaction happen, the reactions are known as electrochemical reactions.

Question 3.
What are Conductors ?
Answer:
Conductors : A substance which allows the electric current to flow through it is called a conductor, e.g. Cu, Ag, Al etc.

Question 4.
What are Non-conductors ?
Answer:
Non-conductors : A substance which does not allow the electric current to flow through it is called a non-conductor, e.g. wood, glass, rubber etc.

Question 5.
What are Metallic conductors ?
Answer:
Metallic conductors These are the substances (metals) which allow the current to pass through them but do not undergo any change in themselves, e.g. Cu, Ag, Au etc.

Question 6.
What are Non-metallic conductors ?
Answer:
Non-metallic conductors These are the substances (non-metals) which allow the current to pass through them but do not undergo any change in themselves, e.g. Graphite, gas-carbon etc.

Question 7.
What are Electrolytic conductors or Electrolytes ?
Answer:
Electrolytic conductor or electrolytes : These are compounds which in the fused state on in solution in a suitable solvent (particularly water) conduct an electric current and undergo distinct chemical decomposition during the process of conducting current. e.g. aque­ous solution of H₂SO₄, NaOH, NaCl etc.

Question 8.
What are Non-electrolytes ?
Answer:
Non-electrolytes : These are substances which do not conduct electricity either in solution or in molten state, e.g. solutions of sugar, urea etc. or liquids like kerosine, alcohol etc.

Question 9.
Why is mercury considered as non-electrolyte ?
Answer:
Explanation: Mercury is a liquid metal. It conducts electricity but during passage of electric current, it is not decomposed. So it is considered as non-electrolyte.

Question 10.
What is Electrolysis ?
Answer:
Electrolysis : The process of chemical decomposition of an electrolyte in solution or in fused state by the passage of electric current is called electrolysis.

Question 11.
State two points of difference between conduction of electricity through a metallic conductor and through an electrolytic substance.
Answer:
Difference between conduction of electricity through metals (also non-metals like graphite, gas carbon) and electrolytes.

Metals (also non-metals like graphite, gas carbon)	Electrolytes
(i)  Metals conduct electricity in solid state, except liquid mercury. (ii) Passage of electricity through these causes physical changes like, heating increase of electrical resistance.	(i)  Electrolytes conduct electricity in solution or in used states. (ii) Electricity through these causes chemical decomposition, which is a chemical change.

Question 12.
What are called Electrodes?
Answer:
Electrodes : The two metallic or graphite strips or rods, placed in a voltameter to pass electric current through the electrolyte during electrolysis are known as electrodes.

Question 13.
What is called Electrolytic dissociation?
Answer:
Electrolytic dissociation : The spliting up of an electrolyte into ions is known as electrolytic dissociation. This is a reversible process. This means that the electrolyte molecules break up partly into ions and the ions in solution constantly reunite to form the undissociated molecules.

Question 14.
Why pure water does not conduct electricity? In what condition does it conduct electricity ?
Answer:
Explanation : In an electrolyte, positive and negative ions conduct elec­tricity. Pure water is a very weak electrolyte in which a very small number of water molecules remain dissociated into H^⊕ and OH^– ions which can conduct electricity. That is why pure water does not conduct electricity.
Condition : To increase conductivity of water a few drops of H₂SO₄ or an alkali or small amount of NaCl is mixed with it so that positive and negative ions, the carrier of electricity, increase.

Question 15.
What is Electrolytic conduction ?
Answer:
Electrolytic conduction : The movement of ions towards oppositely charged electrodes is known as electrolytic conduction.

Question 16.
In electrolysis of water which material are the electrodes made of? Write down the reaction occuring in the electrolyte before electrolysis. Also write down the reactions taking place at cathode and anode during electrolysis.
Answer:
Electrolysis of water :
(i) Electrodes used : Both electrodes (cathode and anode) Pt.
(ii) Name of electrolytes : Water acidified with a few drops of H₂SO₄

Question 17.
Illustrate the process of electrolysis of aqueous copper sulphate solution (using Pt-electrode).
Answer:
Electrolysis of aqueous CuSO₄ (using Pt-electrode) :
Electrodes : Pt (both)
Electrolytes : Aqueous solution of CuSO₄

Question 18.
Illustrate the process of electrolysis of aqueous copper sulphate solution (using Cu, attackable electrodes).
Answer:
Electrolysis of aqueous CuSO₄ (using Cu, attackable electrodes)
(i) Electrodes : Cu(both)
(ii) Electrolytes : Aqueous solution of CuSO₄
(iii) Before electrolysis :

(iv) During electrolysis :
At cathode : Cu²⁺ + 2e → Cu↓
At anode : Cu – 2e → Cu²⁺
As a result, anode Cu-plate goes on losing its weight while that of cathode Cu-plate goes of gaining its weight. The concentration of CuSO₄, solution (electrolyte) in voltameter remains the same.

Question 19.
How cations and anions are discharged at their respective electroles ?
Answer:
The arrangement of cations discharged at cathode (according to electro chemical series)

The arrangement of anions discharged at anode (according to electrochemical series)

Question 20.
What is electroplating ? What is its aim ?
Answer:
Electroplating : It is an art of depositing a superior metal like gold, silver etc. on baser metals like iron, copper etc. through electrolysis.
Aim of electroplating :

• Decoration
• Repairs
• Protection

Question 21.
What are the conditions for good deposit ?
Answer:
Conditions for good deposit :

• High current density
• Low temperature
• High metal concentration in electrolyte
• Electrolyte must be complex salt of the metal to be deposited.

Question 22.
What are the application of electrolysis ?
Answer:
Application of electrolysis :

• Electroplating
• Electro-refining of metals
• Electro-typing
• Extraction of metals

Question 23.
Explain electroplating of Zn.
Answer:
Electroplating of Zn :
Electrolyte : ZnCl₂ solution
\(\mathrm{ZnCl}_2 \rightleftharpoons \mathrm{Zn}^{2+}+2 \mathrm{Cl}^{(-)}\)
Electrodes :
(a) Cathode : the article is to be electroplated
(b) Anode : pure Zn-rod or plate
Reaction at Cathode : Zn²⁺ + 2e → Zn↓

Question 24.
Explain electroplating of Cr.
Answer:
Electroplating of Cr :
(i) Electrolyte :

(ii) Electrodes :
(a) Cathode : the articles is to be electroplated.
(b) Anode : pure Cr-plate
(iii) Reaction at cathode : Cr³ + 3e → Cri↓

Question 25.
Explain electroplating of Sn.
Answer:
Electroplating of Sn :
Electrolyte :

Electrodes :
(a) Cathode : the article is to be electroplated
(b) Anode : pure Sn-plate
Reaction at cathode : Sn² + 2e → Sn↓

Question 26.
Explain electroplating of Cu.
Answer:
Electroplating of Cu :
Electrolyte :

Electrodes :
(a) Cathode : the article is to be electroplated
(b) Anode : pure Cu-plate
Reaction at cathode : Cu²⁺ + 2e → Cu↓

Question 27.
Explain electroplating of Ag.
Answer:
Electroplating of Ag :
Electrolyte: Potassium argentocyanide solution K[Ag(CN)₂]

Electrodes :
(a) Cathode : the article is to be electroplated
(b) Anode : pure Ag plate
Reaction at Cathode : Ag⁺ + e → Ag↓

Question 28.
Explain electroplating of Au (gold).
Answer:
(i) Electroplating of Au :
(ii) Electrolyte : Potassium aurocyanide K[Au(CN)₂] solution ;

Electrodes :
(a) Cathode : the article is to be electroplated,
(b) Anode : pure Au plate
(iii) Reaction at cathode : Au⁺ + e → Au↓

Question 29.
Explain electroplating of Ni.
Answer:
(i) \(\mathrm{NiSO}_4 \rightleftharpoons \mathrm{Ni}^{2+}+\mathrm{SO}_4^{2-}\)
(ii) Electrodes :
(a) Cathode : the article is to be electroplated
(b) Anode : pure Ni-plate
(iii) Reaction at Cathode : Ni² + 2e → Ni↓

Question 30.
How is copper purified by electrolysis method ?
Answer:
Purification of copper by electrolysis method :
Electrolyte : 15% CuSO₄ solution (aqueous) containing (5-10)% sulphuric acid at 50°C is taken in a voltameter.

Electrodes :
(a) Cathode : pure thin copper plate
(b) Anode : thick impure copper plate

Electrolysis : On electrolysis, copper dissolves from the anode and deposits on cathode. Thus gradually the anode plate wear out and the cathode plate thicken. The copper obtained in the way 99 99% purity.

Reactions : \(\mathrm{CuSO}_4 \rightleftharpoons \mathrm{Cu}^{2+}+\mathrm{SO}_4^{2-}\)
At cathode : Cu²⁺ + 2e → Cu↓
At anode : Cu → 2e Cu²⁺

Question 31.
How is aluminium extracted from electrolysis method ?
Answer:
Extraction of a luminium by electrolysis method :

Electrolytes :
(a) Alumina (Al₂O₃) 20%
(b) Fused cryolite (A1F_B, 2NaF) 60%
(c) CaF₂ 20%

Electrodes :
(a) Cathode : inner lining of carbon of the steel tank
(b) Anode : thick carbon rod suspended into fused electrolyte

Reactions :
(a) At cathode : Al³ + 3e → Al↓
(b) At anode : 3F – 3e → 3F
Al₂O₃ + 6F → 2AlF_S + 3O
6O→ 3O₂↑

Question 32.
Explain why blocks of magnesium are often strapped to the steel hulls of ocean going ships.
Answer:
Explanation: Magnesium due to lower reduction potential does not allow the oxidation of steel hulls i.e. magnesium acts, by cathodic protection to prevent oxidation of the steel by transfering an excess of electrons to the steel.

Question 33.
Sodium reacts with water at ordinary temperature while magnesium reacts with hot water. Give reason.
Answer:
Reason : Sodium being more electro-positive decomposes cold water but magnesium which is less electropositive is decomposed by hot water.

Question 34.
A silver wire is dipped in a solution CuSO₄ in one vessel, while in another vessel, a copper wire is dipped in a solution of AgNO_s. What reactions if any take place in the two vessels ?
Answer:
Explanation :
No reaction will take place in first vessel because Ag has greater reduction potential than Cu.
In second vessel, copper will displace Ag from AgNO₃ and the solution of Cu²⁺ ions
Reaction : Cu + 2Ag⁺ → Cu²⁺ + 2Ag↓

Question 35.
Which of the two is a better conductor and why?
(a) a strong electrolyte
(b) a metal.
Answer:
Explanation : Conductivity of electrolytes is due to ionic mobility while that of metal is due to the movement of electrons. Due to their negligible mass, electrons are better conductors than ions with comparatively large mass. Therefore metals are better conductors than electrolytes.

Question 36.
What is cathodic reduction ? Give one example.
Answer:
Cathodic reduction : The reduction of ions taking place at a cathode of a cell is known as cathode reduction. Example : Reduction of Cu²⁺ ions to Cu at cathode of Daniell cell is an example of cathodic reduction.

Question 37.
Anhydrous HCl is a bad conductor of electricity but aqueous HCl is a good conductor. Why ?
Answer:
Expiation : Being covalent in nature, anhydrous HCl is a bad conductor. However, in aqueous solution, it ionises to give H^⊕ and Cu^– ions which conduct the electricity.

Broad Answer Type Questions 

Question 1.
What are the main points of difference between the metallic conductors an electrolytic conductors?
Answer:
Difference between the metallic conductors and electrolytic conductors :

Metallic conductor

• A metallic conductor has relatively free electrons to move and as such the metallic conduction is caused by the flow of electrons in the conductor.
• The passage of an electric current through a metallic conductor does not involve any transfer of matter.
• A metallic conduction is not accompanied by any chemical change of conduction.

Electrolytic conductor

• Electricity is transported through an electrolyse in a state of fusion or solution not by flow of electrons but by the movement of electrically changed ions.
• Flow of electricity is due to the movement of ions and hence there is transfer of matter.
• An electrolytic conduction is invariably accompanied by chemical changes at the electrodes.

Question 2.
What changes are taking place during the electrolysis of an electrolyte?
Answer:
Changes taking place during the electrolysis of an electrolyte.

• When fused or dissolved in water, electrolyte splits up into oppositely charged particles called ions.
• On passing electric current, the cations migrate towards the cathode while the anions migrate towards the anode.
• The cations on reaching the cathode gain electrons from it and from neutral atoms which get deposited on the cathode.
• The anions on reaching the anode lose electrons and get converted into neutral atoms which may be collected as such or they may undergo some secondary change to from some other products.

 

 

Comprehensive WBBSE Class 10 Physical Science Notes Chapter 6 Current Electricity can help students make connections between concepts.

Current Electricity Class 10 WBBSE Notes

Electric current: Electric current is generally means a continuous flow of electrons, ions or any electrically charged particles through a medium.

Electric current is the rate of flow of charge through any cross-section of a canductor.

\(\left(I = \frac{Q}{t}\right)\)

(I = electric current, Q = total charge flowing, t = time)

Units of electric unit

SI unit : Ampere (A): One ampere of electric current is defined as the one coulomb of charge flowing through any cross section of a conductor in one second.

Nature of electric current: Although electric current has both magnitude and direction, yet it is a scalar quantity, as it does not obey vector laws.

Different types of electric currents are:

Steady direct current: An electric current is called a steady direct current if its magnitude and direction do not change with time.

Variable direct current : An electric current is called variable direct current if its magnitude changes with time but direction remains unchanged.

Alternating current : An electric current is called alternating current if its magnitude changes with time and direction also changes periodically.

Current denisity: Current density of a conductor is the amount of current passing per unit area of the conductor held perpendicular to the flow of charges.

Drift velocity: It is the average velocity with which free electrons in a conductor get drifted in a direction opposite to the direction of the applied electric field.

Mobility of the charge carrier: The ratio of the drift velocity of the electrons or charge carriers and the strength of the applied electric field is called the mobility of the charge carrier.

Canductor: The substances through which electric charge flows easily are known as conductors.

Non-conductor: The substances which do not allow electric charge to pass through them are called non-conductors or insulators.

Electric cell : A device in which electric energy is obtained from the chemical energy is known as electric cell.

Negative electrode: The metal rod in which there is excess of negative charge is called negative electrode of cell.

Positive electrode: The metal rod in which there is excess of positive charge is called positive electrode.

Open circuit: When the electrodes of a cell are not connected by a conductor externally, the cell is said to be in open circuit.

Close circuit: When the electrodes are connected internally with a conductor, the cell is said to be in closed circuit.

Electromotive force (e.m.f): The potential difference between the electrodes of a cell in open circuit is called e.m.f.

Potential difference : It is the electrical condition of a point in an electric field or on a current carrying conductor that indicates whether electrons will flow from it or it from another connected point.

Electrical charge: It is the physical property of a matter that causes it to experience a force when placed near another matter.

When ebonite rod is rubbed with flannel, ebonite rod is negatively charged and at the same time flannel acquires an equal amount of positive change. When a glass rod is rubbed with silk, glass rod is positively charged and the same time the silk acquires an equal amount of negative charge.

Electrostatic series: There is a list of substances called electrostatic series, which roughly shows that the two bodies when selected for rubbing will be charged in such a way that the body appearing earlier in the list is positively charged and that coming later in the list is negatively charged. The series is :
Silk, Human body, Cotton, Wood, Sealing wax, Amber, Resin, Sulphur, Rubber, Ebonite.

Basic properties of electric charge :

• Charges are of two types – positive and negative.
• Like charges repeal each other and unlike charges attract each other.
• The positive and negative charges tend to cancel each other.

Coulomb’s Law: The force between two point charges at rest is directly proportional to the product of the magnitude of the charges and inversely proportional to the square of the distance between them. The force acts along the line joining the two charges and its value depends on the nature of the intervening medium.

\(F \infty \frac{q₁ q}{r^2} or } F = K \frac{q₁ q₂}{r^2}\)

(K = electrostatic force constant or Coulomb’s constant and depends upon the system of units and the medium intervening the charges)

Validity for coulomb’s law :

• It holds basically for the point charges
• It is valid over distance as small as of the order of 10^-15 m to several kilometers.
• It depends on the nature of intervening medium.

Dielectric constant : The dielectric constant or relative permittivity of a medium is the ratio of abslute permittivity of the medium to the absolute permittivity of free space.
Dielectric constant depends on the temperature of the medium.
Dielectric constant of water is about 80, so force between two given charges a given distance apart placed in water is 80 times less than when placed in vacuum or air.

Unit of charge:

SI unit of charge is coulomb (c): One coulomb is such a point charge which when placed in vacuum are metre apart from another similar point charge of equal strength repel one another with a force of 9 × 10⁹ N

CGS unit of charge is electrostatic unit (esu): One electrostatic unit of charge is such a point charge which when placed in vacuum one centimetre apart from another similar point charge of equal strength repel one another with a force of one dyne.

1 coulomb = 3 × 10⁹ esu charge

Electric potential: Electric potential at a point in the electric field is defined as the work done per unit charge in moving a unit positive test charge from infinity to that point against the electrostatic force of the field irrespective of the path followed.

Unit of electric potential :

SI unit : Volt (c) : The potential at point is one volt if one joule of work is done in moving one coulomb of charge from infinity to that point in an electric field.

CGS unit: Siat Volt : Potential at a point is one stat volt if one erg of work is done in moving one stat coulomb of charge from infinity to that point in the electric field.

1 stat volt = 300 volt

Potential difference between two points: Potential difference between any two points in an electric field is the work done per unit charge is moving a unit positve charge from one point to the other against the electrostatic force of the field irrespective of the path followed.

Unit of potential difference :

• SI unit : Volt
• CGS unit : Stat volt

Ohm’s Law (1826) : The temperature and other physical condition remaining constant, the current flowing through a conductor is directly proportional to the potential difference across the ends of the conductor.

V ∝ I or, V = RI

Graphical representation of Ohm’s Law: The variation of V and I for two conductors A and B is shown in fig(a). These are straight line having constant

slope = \(\frac{V}{I}\) = R

So, higher the slope means the higher resistance of the conductor. Thus we find B has higher resistance R than that of A.

In the same way fig(b) shows variation of I and V for these two conductors A and B.

Here slope \(\frac{1}{V}\) = \(\frac{1}{R}\), shows that larger the slope, smaller is the value of the resistance of the conductor.

Ohmic conductors : Ohm’s law is found to be valid for a wide range of current and potential in all the metallic conductors and also in some other materials. These conductors are called ohmic conductors.

Non-Ohmic conductors: When the Ohm’s law is found not to be applied for conduction of electricity through vacuum tube, semiconductors and also to electric discharge through gases at low pressure. These are called non-ohmic conductors.

Resistance : The resistance of a conductor is the opposition offered by it to the flow of electric current through it

R = \(\frac{V}{I}\)

(R = resistance of a conductor
V = Potential difference
I = current flowing through a conductor)

Resistivity or specific resistance : The resistivity or specific resistance of the material of a conductor is numerically equal to the resistance between the opposite faces of a unit cube when current flows normally to the faces.

• Unit of Resistivity :
• Ohm-centimetre (Ω-cm)
• Ohm-metre (Ω-m)

Resistance of a given conductor depends on the following factors:

• Length of the conductor: The resistance of a given conductor is directly proportional to its length. R ∝ l
• Area of the conductor: The resistance of a given conductor is inversely proportional to its area of cross-section :
• [R ∝ \(\frac{1}{A}\)]
• Nature of the meterial and temperature of the material of the conductor: We have resistivity,

r = \(\frac{R A}{l}\)

Difference between Resistance and Resistivity :

Resistance	Resistivity
i. Resistance of a conductor depends on the nature of the material of a conductor and also on its dimensions.	i. Resistivity of a conductor depends on the nature of the material of a conductor but independent of its dimension.
ii. Resistance is the property of a body.	ii. Resistivity is the property of the material of the body.
iii. Ohm-meter is an instrument for measuring resistance.	iii. Oi.m-meter is the unit of resistivity.
iv. Dimensional formula of resistance (R) = [ML2T-3A-2]	iv. Dimensional formula of resistivity (ρ) [ρ] =[ML3T-3A-2]

Combination resistance: In different electri al circuit more than one resistance are connected together. This is known as resistance.

Series combination : A number of resistances are said to be in series combination if they are connected one after the other in such a way that the same current flows through all the resistance when same potential difference is applied across the combination.

r = r₁ + r₂ + r₃

Parallel combination : A number of resistance are said to be connected in parallel if one end of all the resistances are joined together and the other ends joined to another point such that the potential difference across each resistance is equal to the applied pr ential difference across the combination.

Internal resistance of a cell : Internal resistance offered by the electrolyte and electrodes of a cell when electric current flows through the cell.

Joule’s Laws :

First Law : The amount of heat produced in a conductor in a given interval of time is proportional to the square of the current passed
H ∝ P² (when R and t are kept constant)

Second Law : The amount of heat produced by a given current in a given time is proportional of the resistance of the conductor.

H ∝ R (when I and t are kept constant)

Third Law : The amount of heat produced in a given conductor by a given current is proportional to the time for which the current passes.
H ∝ t (when I and R are kept constant)
Combining the three laws, we have
H ∝ I² R t
(when I, R and t vary)
or, H = \(\frac{I^2 R t}{J}\)
(J = mechanical equivalent of heat
= 4.2 joul/calorie.)
If I be in ampere, R in Ohm, t in second and H in calorie, then
H = \(\frac{I^2 R t}{4 \cdot 2}\)
or, H = 0.24 I² R t calorie

Fuse : For the safety of the electrical gadgets one thin wire made of an alloy of lead (75 %) and tin (25 %) and which has high resistance and low melting is kept in an insulator box of china clay. The thin coil is called fuse wire. The wire is kept in series with the main circuit of the household electrical appliances.

Electric iron: In this a thin but long wire of nichrome is kept coiled and sandwitched betwen two sheets of mica. This is called the heating element of the iron. The element is kept inside two iron plates and the heating element is kept insulated from the external body of the iron. On passing current through the element it gets heated and the iron in turn becomes hot.

Electric heater: In this, a thin and long wire of nichrome, is kept coiled in the spiral grooves of a porcelain block. This block is kept in metallic case and there is arrangement for making electrical connection with two ends of the coil.

Electric bulb : A thin but long coiled coil (filament) of tungsten wire is introduced in evacualed glass blub. Sometimes the bulb is filed with some inert gases. Electric contact to the filament is made by two comparatively thick wires. The resistance of the filament wire is such that it may glow being strongly heated by the electric current.

If a bulb be marked as ‘220 V-60 W’ then we mean that the lamp should be used at a potential difference of 220 Volts and on doing so it will glow fully and electrical energy will be spent at the rate of 60 joules per second or a power of 60 W} will be required.

It should be remembered that although same current through the filament of the bulb and the line wires, the resistance of the filament wire being much larges, the heat (I² R) produced in it is much larger and hence glows brightly. It may be further noted that they resistance of the bulb marked 200 V-100 W is less than another marked 200 V-60 W. As a result more current passes through the coils of the former bulb and more heat (I² R) is produced in it thus glows more brightly.

Units of electrical power and energy :

Watt : The SI unit of electrical power is watt. A watt is the power expended when one ampere of current flows under a potential difference of one volt.

so placed that the current carrying wire lies between the palm and the needle and the palm always facing the wire and the fingers pointing in the direction of the current, then the outstretched thumb will give the direction of deflection of the north pole of the needle.

Magnetic field: The magnetic field at any point in the field is numerically equal to the force experienced by a unit charge moving with a unit velocity perpendicular to the direction of the magnetic field at that point.

Fleming’s left hand rule : If the first finger, the middle finger and the thumb of the left hand be stretched mutually perpendicular to each other in such a way that the first-finger points in the direction of the magnetic field and the middle-finger points in the direction of electric current, then the thumb gives the direction of the force acting on the conductor.

Ampere’s circuital Law : It states that the line integral of magnetic field around any closed path in vacuum is equal to absolute permeability times the total current enclosed by the path.

Moving coll galvanometer : A moving coil galvanometer is an instrument for detection and measurement of small electric current.

Ammeter : An ammeter is a low resistance galvanometer, which is used to measure current in a circuit.

Voltmeter : A voltmeter is a high resistance galvanometer used to measure the potential difference between two points of an electrical circuit.

Diamagnetic substances : Diamagnetic substances are those in which the individual atoms or molecules or ions do not possess any net magnetic moment of their own.

Paramagnetic substances: Paramagnetic substances are those in which each individual atom or molecule or ion has a net non-zero magnetic moment of its own and placing such a material in an external magnetic field, it tries to align the individual dipole moments in the direction of the magnetic field.

Barlow’s wheel: Action of the magnet on a current and how rotational motion can be produced due to this effect can be shown by the experiment on Barlow’s wheel.

Electric motor: The device or machine which converts the electrical energy into mechanical energy is known as Electric Motor.

Solenoid : If many turns an insulated wire would around a cylinder the resulting coil is known as solenoid.

An ammeter has a low resistance and as it is connected in series in a circuit, so it reads slightly less than the actual current.

While giving reading a small current always passes through a voltmeter, so it cannot be used for determining the emf of a cell. For which a potentiometer is used, where at balanced condition no current passes through the cell.

The resistance of an ideal ammeter is zero.
The resistance of an ideal voltmeter is infinity.
The ammeter is a low resistance instrument and connected in series in an electrical circuit.

The voltmeter is a high resistance instrument and connected in parallel across the circuit.

Ferromagnetic substances: Ferromagnetic substances are those in which each individual atom or molecule or ion has a non-zero magnetic moment, same as in a paramagnetic substance.

Magnetic flux: The magnetic flux through any surface held in a magnetic field is measured by the total number of magnetic lines of force crossing the surface.

Faradav’s laws of electromagnetic induction :

First Law : Whenever there is a change in the magnetic flux linked with a coil, an emf is induced in it and its emf lasts as long as the change in the magnetic flux continues.

Second Law : The magnitude of the emf induced in the coil is proportional to the rate of change of magnetic flux linked with the coil.

Lenz’s Law : The induced current will be in such a direction that it opposes the cause which produces it.

Faraday’s law as modified by Lenz’s law: The emf induced in a coil is given by the negative of the rate of change of magnetic flux linking with its turns.

Fleming’s right hand rule: If the first finger, central finger and thumb of the right hand be stretched in the mutually perpendicular directions such that the first finger points along the direction of the field and thumb be along the direction of motion of the conductor, then the central finger would give the direction of induced current. It is also called dynamo rule.

Eddy currents : Eddy currents, first discovered by Foucault in the year 1895, are the currents induced in the body of a conductor when the amount of magnetic flux linked with the conductor changes. After the name of its discoverer, it is also called Foucault current.

Alternating current : An electric current, magnitude of which changes with time and direction reverses periodically is called alternating current (a.c.).

I = I₀ sin ω t or I = I₀ cos ω t

where I is the instantaneous value of current i.e. the magnitude of the current at any instant of time t, I₀ is the peak value or maximum value or amplidue of a.c. and ω is the angular frequency of a.c.

The terms used for alternating current hold equally for alternating e.m.f and may be represented as

E = E₀ sin ω t or E = E₀ cos ω t

where E and E₀ are the instantaneous and maximum or peak value of the alternating emf respectively.

Advantages and disadvantages of a c. over d.c

Advantages of a.c. over d.c. :

• Generation, transmission, distribution of a.c. is more economical and convenient.
• A.C. can be controlled more effectively and easily with very little loss of power by using inductors.
• A.C. can be transmitted with very little loss of power using transformer.
• A.C. can be easily converted in d.c. by using rectifiers.
• Using transformers a.c. voltages can be stepped up or stepped down to any desired value.

Disadvantages of a.c. over d.c.

• A.C is more dangerous than d.c.
• A.C. cannot be used in electrolysis.
• Calibrations of A.C. meters for small measurements are difficult as the markings are not equidistant.
• Conduction of a.c. through metal wires suffer skin effect.

A.C. generator or Dynamo: An a.c. generator or dynamo is an device used to convert mechanical energy into electrical energy.
An a.c. generator works on the principle of electromagnetic induction i.e. when a coil is rotated in uniform magnetic field, an emf is induced in the coil.

The main components of a.c. generator are:

• Armature : It is a coil having a large number of turns of insulated copper wire wound on a soft iron core.
• Field magnet : A strong permanent magnet with cylindrical pole pieces is used as a field magnet. The uniform magnetic field produced by it is perpendicular to the axis of rotation of the coil.
• Slip rings : Two terminals of the armature coil are connected to two slip rings made of brass. These rings rotate with the coil.
• Brushes : There are two carbon brushes touching two slip rings and remain fixed while slip rings rotate along with the coil. The brushes are connected to the output through load.

Following Faraday’s laws of electromagnetic induction, the induced emf produced in the coil given by

E = E₀ sin ω t

D.C. generator or Dynamo: A d.c. generator is similar, in many ways, to an a.c generator. In the internal circuit of a d.c. generator, current is produced in the same way as in the internal circuit of an a.c. generator but the current in the external circuit of a d.c. generator, is unlike that of an a.c. generator, direct and not alternating. The alternating current is converted into direct current by a commutator which is nothing but a pair of semicircular ring. These are called split rings.

Barlow’s wheel : The action of magnet on current and there by rotation of the conductor itself, is demonstrated by Barlow’s wheel.

Factors governing the speed of Rotation :

• Rotational speed increases with current and vice versa.
• Rotational speed increases with intensity of magnetic field and vice versa.
• If alternating current (ac) is used instead of direct current (dc), the wheel wire try to reverse it’s direction with the change in direction of current resulting no rotation.

Factors governing the direcion of Rotation :

The direction of rotation will reverse if direction of current is reverse keeping direction of magnetic field intact.
The direction of rotation will reverse if direction of magnetic field is reversed keeping direction of current intact.
The direction of rotation will remain unchanged if both direction of magnetic field and direction of current are reversed.

Electrical Switch: An electrical switch in any device used to interrupt the flow of electrons in a circuit.

Types of Switch :

Toggle switch : Toggle switches are actuated by a lever angled in one of two or more positions. The common light switch used in household wiring is an example of toggle switch.

Push button switch : Push button switches are two-position devices actuated with a button that is pressed and released most push button switches have an internal spring mechanism returning the button to its ‘out’ or ‘unpressed’ position for momentary operation.

Selector switch : Selector switches are actuated with a rotary knob or lever of some sort to select one of two or more positions.

Joystick swich : A joystick to actuated by a lever free to move in more than one axis of motion.

Lever actuator limit switch : These limit switches closely resemble rugged toggle or selector hand switches fitted with a lever pushed by the machine part.

Proximity switch : Proximity switch sense the approach of a metallic machine part either by a magnetic or high-frequency.

Speed switch : These switches sense the rotary speed of a shaft either by a centrifugal weight mechanism mounted on the shaft or by some kind of non-contact detection of shaft motion such as optically or magnetic.

Pressure switch : Gas or liquid

pressure can be used to actuate a switch mechanism if that pressure is applied to a piston, diaphram, or bellows with converts pressure to mechanical force.

Socket : Socket may refer to

In machanics

• Socket wrench : A type of wrench that uses separate, removable sockets to fit different sizes of nuts and bolts.
• Socket head screw: A screw (or bolt) with a cylindrical head containing a socket into which the hexagonal ends of an Allen wrench will fit.
• Socket termination : A termination used at the ends of wire rope.

In biology :

• Eye socket: A region in the skull where the eyes are positioned.
• Tooth socket: A cavity cantaining a tooth, in those bones that bear teeth.
• Dry socket: A painful opening as a result of the blood not clotting after a tooth is pulled.0
• Ball and socket joinf.

In computer networking :

• Networking socket : an end-point in a communication across a network or the internet.
• Unix domain socket : an end point in local inter-process communication.

Electrical and electronic connectors :

• AC power plugs and sockets : Electrical devices used to connect to a power source onto which another device can be plugged or screwd in.
• Antenna socket, a female antenna connector for television cable.
• CPU socket : The connector on a computer’s motherboard for the CPU.
• Jack (connector) : One of several types of electronic connectors.
• Lamp socket : A connector into which a light bulb screws.

Live wire, neutral wire: An electric current is a flow of electric charge. Most mains powered appliances need three wires to work safely. They are live, neutral and earth.

Only two of the wire are used when the appliance works properly. These are the live (brown) and the neutral (blue) wires. The live wire carries current to the appliance at a high voltage. The neutral wire completes the circuit and carries current away from the appliance. The third wire called the earth wire (green/yellow) is a sefely wire and connects the metal case of the appliance to the earth. This stops a fault making the case of the appliance live.

Earthing: If a fault occurs where the live wire connects to the case the earth wire allows a large current to flow through the live and earth wires. This overheats the fuse which melts and breaks the circuit appliance such as hairdryers are said to be ‘double insulated’ and there’s no need for an earth wire because the case is made of a non conducting plastic. If a faulty live wire touches the inside of the plastic case there’s little risk as the case is an insulator.

Main switch (Isolator): The 100 A rated main switch is a switch disconnector which can be used as an Isolator, and can be used for residential and light commercial applications.

The operating switch can be locked in the ON or OFF position, using a device lock. The main switch has a positive contact status indicator, i.e. when green window is visible this indicates that there is a 4 mm contact gap.

Diagram showing Domestic wiring : Generally the live wire is red, neutral wire is black and earth wire is green in domestic electrical wiring. All appliances are kept in parallel through a switch so as to ensure 220 volt across all appliances. Each appliance should be provided with separate switch.

Detailed explanations in West Bengal Board Class 10 Physical Science Book Solutions Chapter 8.2 Ionic and Covalent Bondings offer valuable context and analysis.

WBBSE Class 10 Physical Science Chapter 8.2 Question Answer – Ionic and Covalent Bonding

Very Short Answer Type Questions :

Question 1.
What is a chemical bond?
Answer:
Chemical bond is a strong force of attraction that holds together atoms in a molecule or crystal.

Question 2.
What is the electronic configuration of noble gases in their valence shell ?
Answer:
Noble gases (except helium) have eight electrons in their valence shell i.e. they have ns², np⁶ configuration.

Question 3.
Why noble gases are inert?
Answer:
The inert nature of noble gases is due to their stable electronic configuration.

Question 4.
How does electrovalency occur?
Answer:
Electrovalency occurs due to shifting of electron.

Question 5.
What is the common reason behind the phenomena of electron release and electron sharing by elements?
Answer:
This is due to the tendency of elements to attain stable state of their nearest elements in periodic table.

Question 6.
What type of valency would be exhibited when an element combines with sodium ?
Answer:
Electrovalency.

Question 7.
Why are electrovalent compounds generally solid ?
Answer:
Electrovalent compounds are generally solid due to strong attractive electrostatic force between ions of opposite charges.

Question 8.
How is the valency of an element in an electrovalent compound measured ?
Answer:
The valency of an element in an electrovalent compound is measured by the number of electrons gained or lost by one atom of the element.

Question 9.
Name a covalent compound.
Answer:
Water (H₂O) is covalent compound.

Question 10.
Name an electrovalent compound.
Answer:
Sodium chloride (NaCl) is an electrovalent compound.

Question 11.
Name the type of valency where electrons are shared ?
Answer:
Electrons are shared in covalency.

Question 12.
Which class of substance is a common component of all electrovalent compounds ?
Answer:
A metal is common component of all electrovalent compounds.

Question 13.
State one characteristic of covalent compounds.
Answer:
Covalent compounds do not produce ions in solution or in fused states, so these are non-electrolytes.

Question 14.
What is the valency of carbon in CH₄ compound?
Answer:
The valency of carbon is 4 in CH₄ compound.

Question 15.
What is the nature of ionic bond ?
Answer:
Tonic bond is non-directional in nature.

Question 16.
SnCl₄ is a poor conductor of electricity. Why ?
Answer:
SnCl₄ being a covalent compound does not ionise and hence is a poor coductor of electricity.

Question 17.
What is the C – C bond length in saturated compounds ?
Answer:
The C-C bond length in saturated compounds is 1.54A°

Question 18.
What is the structure of ammonia ?
Answer:
The structure of ammonia is pyramidal.

Question 19.
What is the nature of bond formed between Cs and F ?
Answer:
The nature of bond formed between Cs and F is ionic.

Question 20.
Name of compound which contains both ionic and covalent bond.
Answer:
Potassium cyanide (KCN)

Question 21.
How many electrons take in forming bonds in N₂ ?
Answer:
The total number of electrons that take part in forming bonds in N₂ is 6.

Question 22.
Name the element which has highest electronegativity.
Answer:
‘F’ has highest electronegativity (4.0).

Question 23.
Consider two elements with atomic no. 37 and 53. What will be the bond between their atoms?
Answer:
Covalent.

Question 24.
What will be the shape of ethane?
Answer:
The shape of ethane is tetrahedral.

Question 25.
What is the type of bonding in ferric chloride ?
Answer:
The lype of bonding in ferric chloride is covalent.

Question 26.
Name an element which has zero electronegativity?
Answer:
Helium has zero electronegativity.

Question 27.
How many lone pair(s) is/are present XeOF₄ ?
Answer:
1 (one).

Question 28.
On which does lattice energy of an ionic compound depend ?
Answer:
Lattice energy of an ionic compound depends upon charge and size of the ion.

Question 29.
Give the name of one electrovalent substance which is used in everyday life.
Answer:
Sodium chloride (NaCl)

Question 30.
Give the name of one covalent substance which is used in everyday life.
Answer:
Water (H₂O).

Question 31.
Which one of NaCl and C₆ H₁₂ O₆ will have higher melting point?
Answer:
NaCl.

Question 32.
What types of bonds are expected between hydrogen atom and chlorine atom is HCI(g) molecule ?
Answer:
Covalent.

Question 33.
Atomic numbers of two elements A and B are 20 and 17 respectively. What would be the nature of the bond (covalent or electrovalent) between them if they combine chemically among themselves ?
Answer:
Electrovalent.

Question 34.
How many electrons are there in the outermost shell of the atom of the element carbon?
Answer:
four (4).

Question 35.
Between MgCl₂ and CHCl₃ which one is electrovalent in nature?
Answer:
MgCl₂.

Question 36.
What do you mean by valence shell ?
Answer:
The outermost shell of an atom is known as valence shell.

Question 37.
What is the nearest inert element of chlorine atom ?
Answer:
The nearest inert element of chlorine atom is argen (Ar).

Question 38.
What is the valency present in NaH ?
Answer:
Electrovalency is present in NaH.

Question 39.
What is the nearest inert element of carbon ?
Answer:
The nerest inert element of carbon is neon (Ne).

Question 40.
What are the types of Covalent bond ?
Answer:
Covalent bonds are of three types.
They are : (i) Covalent single bond (ii) covalent double bond (iii) coval at triple bond

Question 41.
What kind of bonding is present in substances which are nonelectrolytes?
Answer:
Covalent Bonding

Question 42.
The lonic crystals are always brittle-why?
Answer:
If mechanical pressure is applied to an ionic crystal then ions of similar charges may be forced to get closer to each other. By doing so, the electrostatic repulsion can be enough to split or disorient the lattice structure completely. This imparts brittleness to the structure.

Question 43.
Who proposed the electron dot structures to describe the bonding in simple covalent compounds ?
Answer:
Lewis proposed the electron dot structures to describe the bonding in simple covalent compounds.

Question 44.
Which bond has directional property?
Answer:
Covalent bonds have directional property.

Question 45.
Ionic bonds are non-directional in nature why?
Answer:
The attractive forces between ions in ionic compounds expend equally in all possible directions. It acts neither in a specific direction nor in confined to two particular ions. So, ionic bonds are non-directional in nature.

Question 46.
Give example of a covalent compound which can conduct electricity in aqueous solution.
Answer:
Hydrogen chloride ( HCl), though a covalent compound, undergoes complete ionization in water and conducts electricity in its aqueous solution.

Question 47.
Write the name of an ionic compound in which both the atoms of the component elements do not have octet.
Answer:
Lithium hydride (LiH) is the ionic compound in which both Li and H have duplet and not octet.

Question 48.
Sulphur is soluble in carbon disulphide but insoluble in waterexplain why?
Answer:
Carbon disulphide is a non-polar solvent and water is a polar solvent. Sulphur, being a covalent element molecule, is therefore soluble in non-polar carbon disulphide but not in water.

Short Answer Type Questions :

Question 1.
What are the causes of chemical combination ?
Answer:
Cause of chemical combination :
(i) Tendency to acquire noble gas configuration.
(ii) Tendency to acquire minimum energy.

Question 2.
What are the common types of bonds ?
Answer:
Depending upon the mode of acquiring nerest noble gas configuration, there are three common types of bonds :
(i) Ionic or Electrovalent bond, (ii) Covalent bond and (iii) Co-ordinate or Dative bond.

Question 3.
What are the main types of physical bonds ?
Answer:
The main types of physical bonds are : (i) Hydrogen bond, (ii) Metallic bond, (iii) Van der Waal’s interactions

Question 4.
What is the electronic theory of bonding ?
Answer:
Electronic theory of bonding : Atoms combine by transfer of electrons (ionic bonding) or by sharing of electrons (covalent bonding).

Question 5.
What is lonic bonding ?
Answer:
Ionic bonding : The electrostatic force of attraction which holds the oppositely charged ions together is called ionic bond or electrovalent bond and the compounds which are formed by the transference of electrons from one atom to other are known as ionic or electrovalent compounds. The number of electrons which an atom loses or gains while forming an ionic bond is known as electrovalency.

Question 6.
What are the conditions necessary for the formation of lonic bond ?
Answer:
Conditions necessary for the formation of Ionic bond :

1. Formation of cation from a neutral atom having low ionisation energy.
2. Formation of an anion from a neutral atom with high value of electron affinity.
3. Formation of crystal lattice from oppositely charged ions involving large release of energy.

Question 7.
What is Lattice energy ?
Answer:
Lattice energy : Lattice energy of an ionic solid is the amount of energy released when required number of cations and anions combine to form one mole of an ionic solid.

Question 8.
What are the factors by which Lattice energy depends ?
Answer:
Lattice energy depends upon the following factors :

1. Magnitude of charge of ions : It increases with increase in charge on cation, anion or both.
2. Size of cation : For a common anion, the lattice energy decreases with increase in size.
3. Size of anion : For a common cation, the lattice energy decreases, with increase size of anion.

Question 9.
What are the characteristics of ionic compounds ?
Answer:
Characteristics of ionic compounds :

1. All ionic compounds are usually crystalline solids and are composed of ions even in the solid state.
2. Ionic solid have high melting points and boiling points due to the presence of strong attractive forces between the oppositely charged ions.
3. Ionic compounds have low volatility high density and high stabiliy.
4. lonic compounds are highly soluble in polar solvents (such as water) having high dielectric constant (80) but insoluble in organic solvents (such as benzene, alcohol. ether etc.)

Question 10.
What type of valency is shown when sodium combines chemically with chlorine?
Draw the relevant electron dot diagram.
Answer:
Electrovalency is shown when sodium combine chemically with chlorine.
Electron dot diagram :

Question 11.
State the common reason behind the phenomena of electron release or electron capture by atoms to form ions.
Answer:
Explanation : An element goes into chemical bondage with another element since it tends to attain the stable state of its nearest inert element in the periodic table. To fulfill this, an atom either gains or loses electrons to possess 8 electrons or 2 electrons (for hydrogen atoms) in its outermost orbit. As a result of losing electrons, atoms are transformed to positive ions and on gaining electrons atoms transform to negative ions.

Question 12.
What type of valency is shown in Li₂O ? Draw the relevant electron dot diagram.
Answer:
Li₂ O Shows electrovalency.
Electron dot diagram :

Question 13.
What type of bonding is present in CaO ?
Answer:
Ionic bonding is present in CaO
Electron dot diagram :

Question 14.
What type of bonding is present in MgCl₂ ?
Answer:
Ionic bonding is present in MgCl₂
Electron dot diagram :

Question 15.
What type of valency is shown in Al₂ O₃ ?
Answer:
Flectron dot diagram :

Question 16.
What is covalent bond?
Answer:
Covalent bond (G.N. Lewis, 1916): A covalent bond is formed by the mutual sharing of electrons between the atoms, both of which are short electrons. The compound so formed is called covalent compounds. The member of electrons contributed by an atom for sharing is known as its covalency. Depending upon the number of electrons shared between two atoms being one, two or three, we have single covalent bond (: or = ), double covalent bond (:: or = ) and triple covalent bond ( :: or ≡ ).

Question 17.
What is octet rule ?
Answer:
Octet rule It states that atoms react because they have a tendency to complete their octet (or duplet) i.e. to have eight electrons in the valence shell (or two electrons if only one shell is present). They can do so by losing, gaining or sharing electrons.

Question 18.
What are the exceptions of octet rule ?
Answer:
Exceptions of octet rule There are many atoms which do not obey the octet rule and may contain six (as in BF₃ ), ten (as in PF₃ ) electrons.

Question 19.
What are the characteristics of covalent compounds?
Answer:
Characteristics of covalent compounds :

1. Covalent compounds exist in solid, liquid and gaseous state.
2. These compounds have low melting and boiling points.
3. These (except graphite) are bad conductors and react slowly.
4. These are soluble in non-polar solvents such as benzene, acetone etc., but are insoluble in polar solvents such as water.
5. Due to the directional nature of covalent bonds, these compounds show stereoisomerism.

Question 20.
What type of bonding is present in nitrogen molecule ?
Answer:
Covalent bonds are present in nitrogen molecule :
Diagram :

Question 20.
What type of bonding is present in oxygen molecule ?
Answer:
Covalent bonds are present in oxygen molecule.
Diagram :

Question 21.
What type of bonding is present in hydrogen molecule ?
Answer:
Covalent bond is present in hydrogen molecule.
Diagram :

Question 22.
How HCl(g) molecule is formed ?
Answer:
Covalent bond is present in HCl(g) molecule.
Diagram :

Question 23.
How water molecule is formed ?
Answer:
There are two covalent bonds in water molecule.
Diagram :

Question 24.
How methane molecule is formed?
Answer:
These are four covalent bonds in methane molecule.
Diagram :

Question 25.
How ammonia molecule is formed ?
Answer:
These are three covalent bonds in ammonia molecule.
Diagram :

Question 26.
How carbon dioxide molecule is formed ?
Answer:
These are four covalent bonds present in carbon dioxide molecule.
Diagram :

Question 27.
Why does the tendency of sharing electrons grows in many nonmetallic atoms during formation of covalent compounds ?
Answer:
Explanation : During formation of covalent compounds of non-metallic atoms, each participant involved in the process tends to attain duplet or octet stable state. To attain such stable state they share electrons.

Question 28.
Writ town the electronic configuration of a chlorine atom, a chlorine ion.
Answer:
Electronic configuration of chlorine atom is : 2, 8, 7.
Electronic configuration of a chlorine ion is : 2, 8, 8.

Question 29.
What is co-ordinate bond or dative bond ?
Answer:
Co-ordinate bond : It is a special type of covalent bonding where the shared pair of electrons is supplied only by one of the atoms forming the bond. The atom which supplies the shared pair of electrons is called donar while the atom which only uses the shared pair of electrons is called acceptor. e.g. Ammonium ion (\(\mathrm{NH}_4⁺}\))

Question 30.
SnCl₄ is a poor conductor of electricity. Why ?
Answer:
Explanation SnCl₄ being a covalent compound does not ionise and hence, is a poor conductor of electricity.

Question 31.
Covalency possesses directional properties but electrovalency has no such characteristics. Why ?
Answer:
Explanation Shared electron pairs of covalent bonds are localised between two atoms. Hence covalent bonds have directional character on the other hand oppositely changed ions in electrovalent compounds are held together by electrostatic forces of attraction which in non-directional in nature.

Question 32.
HCI gas is a covalent compound but its water solution conducts electricity. Why ?
Answer:
Explanation Electro-negativity of Cl and H are 3 and 2.1 respectively. The difference in the electro-negativities of Cl and H being 0.9, the bond in HCl is a polar covalent bond. When gaseous HCl is dissolved in water, then due to high dielectric constant of water (80), it breaks apart, the positive and negative ends of the dipole in HCl molecule giving H₃ O⁺ and Cl^– ions which conduct electricity.
HCl(g) + H₂O(l) → H₃O⁺ (aq) + Cl^– (aq)

Question 33.
Amongst LiF and Lil which has more covalent character and why ?
Answer:
Explanation : Lil has more covalent character because Li⁺cation will be able to polarize the bigger I^–more than the smaller F^–ion. Greater polarisation in Lil leads to more covalent character.

Question 34.
Water is generally a good solvent for lonic compounds. Why ?
Answer:
Explanation : Dielectric constant of water being high (80), the electrostatic force of attraction between oppositely charged ions gets reduced to (1/80) of original force in air. Hence, ions of an electrovalent compound get separated which then solvated by waters.

Broad Answer Type Questions: 

Question 1.
What is the difference between ionic compounds and covalent compounds ?
Answer:
Difference between ionic and covalent compounds :

Ionic Compounds	Covalent Compounds
i. These are formed by the transfer of one or more electrons from one atom to another.	i. These are formed by the sharing of one or more electrons between the bonded atoms.
ii. These consist of ions.	ii. These consist of individual molecules.
iii. These are soluble in water but insoluble in organic solvents.	iii. These are insoluble in water but soluble in organic solvents.
iv. These are hard solids with high melting and boiling points.	iv. These exist as gases, liquids or soft solids with low melting and boiling points.
v. These undergo ionic reactions which are very fast.	v. These undergo molecular reactions which are very slow.
vi. These conduct electricity in fused as well as aqueous solutions.	vi. These do not conduct electricity.
vii. These do not show isomerism.	vii. These show isomerism.

Question 2.
The atomic number of the element A is 20 and that of another element B is 17. Write down their electronic configurations. Will they produce an electrovalent compound or a covalent compound ? What will be their valencies in that case?
Answer:
Electronic configuration of A is : 2,8,8,2.
Electronic configuration of B is : 2,8,7.
They will produce and electrovalent compound.
Explanation . An atom A will give up two (2) valence electrons, each of two atoms of B will capture one electron. In the process atoms of A and B attain stable octet state and atoms of A will be positive ions and those of B will be negative ions. A and B thus form electrovalent compound.
As, an atom of A loses two electrons. So A has valency 2 (two) and since each atom of B captures one electron, the valency of B will be one (1).

Question 3.
Write down electronic arrangement of the element \({ }_{17}^{35} \mathrm{X}\)
1. what is the valency of the element?
2. will the element form anion or cation?
3. what type of valency will be exhibited when the element combines with sodium?
Answer:
The electronic configuration of the element X is : 2,8,7,

1. As an atom of the element tends of capture or share one electron to attain stable of octet, its valency is 1.
2. It will form anion by capturing electron.
3. The element will exhibit electro-valency when it combines with sodium since sodium is a metal, and atom of which tends to release one electron.