Class 10

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.

Well structured WBBSE Class 10 Physical Science MCQ Questions Chapter 8.1 Periodic Table and Periodicity of the Properties of Elements can serve as a valuable review tool before exams.

Periodic Table and Periodicity of the Properties of Elements Class 10 WBBSE MCQ Questions

Multiple Choice Questions :

Question 1. The basis of modern periodtc table is :
(A) atomic volume
(B) atomic number
(C) atomic weights
(D) atomic size
Answer:
(A) atomic volume.

Question 2.
Which of the following has the maximum value of electron affinity?
(A) F
(B) Cl
(C) Br
(D) I
Answer:
(B) Cl

Question 3.
The elements of group IIA and IIA are known as :
(A) s-block elements
(B) p-block elements
(C) typical elements
(D) transition elements
Answer:
(A) s-block elements

Question 3.
Characteristic of transition elements is incomplete :
(A) d-orbitals
(B) f-orbitals
(C) p-orbitals
(D) s-orbitals
Answer:
(A) d-orbitals

Question 4.
The electron affinity of inert gases is likely to be :
(A) high
(B) negative
(C) positive
(D) zero
Answer:
(D) zero

Question 5.
The element with the highest first ionization potential is :
(A) boron
(B) carbon
(C) nitrogen
(D) oxygen
Answer:
(C) nitrogen

Question 6.
In second period, if we move from Li to F, there is regular decrease in :
(A) atomic mass
(B) atomic radius
(C) electronegativity
(D) ionization potential
Answer:
(B) atomic radius

Question 7.
Compared to the first ionisation potential of an atom, the second is:
(A) the same
(B) greater
(C) smaller
(D) negligible
Answer:
(B) greater

Question 8.
Which has the largest first ionization energy ?
(A) Li
(B) Na
(C) K
(D) Rb
Answer:
(A) Li

Question 9.
The outermost electronic configuration of the most electronegative element is :
(A) ns² np³
(B) ns² np⁴
(C) ns² np⁵
(D) ns² np⁶
Answer:
(C) ns² np³

Question 10.
Which one of the following has the largest size ?
(A) Br^–
(B) I^–
(C) I
(D) \(I^{\oplus}\)
Answer:
(B) I

Question 11.
Which one of the following is the smallest in size ?
(A) N^3-
(B) O^2-
(C) F^–
(D) Na⁺
Answer:
(D) Na

Question 12.
All the elements in a group in the periodic table have the same:
(A) atomic weight
(B) atomic number
(C) number of electrons available for bonding
(D) atomic mass
Answer:
(C) number of electrons available for bonding.

Question 13.
‘The law of triads’ is applicable to the following :
(A) Cl, Br, I
(B) H, O, N
(C) Na, Ne, Ca
(D) None of the above
Answer:
(A) Cl, Br, I

Question 14.
The element in the third group and third of periodic table is :
(A) B
(B) Na
(C) Al
(D) Mg
Answer:
(C) Al

Question 15.
The law of octaves applies to :
(A) B, C, N
(B) As, K, Ca
(C) Be, Mg, Ca
(D) None of the above
Answer:
(C) Be, Mg, Ca

Question 16.
In which group of the periodic table will the element with atomic number z=17 occur ?
(A) IA
(B) IIIB
(C) VIIB
(D) VIB
Answer:
(C) VIIB

Question 17.
Pnicogens are the elements belonging to the :
(A) 12 group
(B) 13 group
(C) 15 group
(D) 16 group
Answer:
(C) 15 group

Question 18.
5f-subshell is successively filled up in :
(A) actinoids
(B) lanthanoids
(C) trypical metals
(D) normal metal
Answer:
(A) actinoids

Question 19.
In the long form periodic table, the block containing non-metals is:
(A) s
(B) p
(C) d
(D) f
Answer:
(B) p

Question 20.
Variable valency is shown by :
(A) typical elements
(B) normal elements
(C) transition elements
(D) none of the above
Answer:
(C) transition eleme is

Question 21.
Which of the following form coloured salts ?
(A) non-metals
(B) metals
(C) p-block elements
(D) transition elements
Answer:
(D) transition elements

Question 22.
Which of the following does not reflect the periodicity of elements :
(A) Bonding behaviour
(B) Electronegativity
(C) Ionisation-potential
(D) Neutron/proton ratio
Answer:
(D) Neutron prolon ratio

Question 23.
Zero group wasjntroduced by
(A) Lother Meyer
(B) Mendeleev
(C) Ramsay
(D) Locker
Answer:
(C) Ramsay

Question 24.
The telluric helix was given by :
(A) Newlands
(B) Lother Meyer
(C) Mendeleev
(D) De Chancourtois
Answer:
(D) De Chancourtois

Question 25.
Lithium shows diagonal relationship with :
(A) Ne
(B) Mg
(C) Be
(D) Ce
Answer:
(B) Mg.

Question 26.
The number of elements discovered till date is :
(A) 63
(B) 109
(C) 60
(D) 118
Answer:
(D) 118

Question 27.
At the time of publication of Mendeleev’s periodic table the number of inert gas elements discovered are :
(A) 1
(B) 8
(C) 3
(D) 0
Answer:
(D) 0

Question 28.
How many periods are there in the Mendeleev’s periodic table ?
(A) 7
(B) 10
(C) 6
(D) 14
Answer:
(A) 7

Question 29.
The similarity between the subgroup A and B elements is with respect to their :
(A) physical properties
(B) chemical properties
(C) valency
(D) none
Answer:
(C) Valency

Question 30.
Long form of periodic table based on :
(A) atomic number
(B) atomic mass
(C) number of neutrons
(D) none of these
Answer:
(A) atomic number

Question 31.
Which period contains the greatest number of metals?
(A) 1
(B) 2
(C) 3
(D) 4
Answer:
(D) 4

Question 32.
Which of the following elements belongs to the group that includes the most active metals?
(A) Aluminium
(B) Sodium
(C) Iron
(D) Mercury
Answer:
(B) Sodium

Question 33.
At the end of each period the valence shell is
(A) incomplete
(B) half filled
(C) singly occupied
(D) completely filled
Answer:
(D) completely filled

Question 34.
Hydrogen is called ?
(A) rogue element
(B) noble element
(C) transuranic element
(D) rare earth element
Answer:
(A) rogue element

Question 35.
Which of the following is a transuranic element ?
(A) Radium
(B) Neptunium
(C) Thorium
(D) Actinium
Answer:
(B) Neptunium

Question 36.
An element in second period whose electron affinity is zero is :
(A) Helium
(B) Argon
(C) Neon
(D) Krypton
Answer:
(C) Neon

Question 37.
Group 17 elements are also called as :
(A) alkali metals
(B) transition metals
(C) chalcogen
(D) halogen
Answer:
(D) halogen

Question 38.
which of the given elements A, B, C, D and E with atomic number 2,3,7,10 and 30 respectively belong to the same period?
(A) A, B, C
(B) B, C, D
(C) A, D
(D) A, C, E
Answer:
(B) B, C, D

Question 39.
The correct order of ionization potential is :
(A) Mg > Ar > Si
(B) Mg < Ar < i
(C) Mg > Si > Ar
(D) Mg < Si < Ar
Answer:
(D) Mg < Si < Ar

Question 40.
Which one is not a Dobereiner’s triad?
(A) Li, Na, K
(B) C, Si, Ge
(C) Ca, Sr, Ba
(D) Cl, Br, I
Answer:
(B) C, Si, Ge

Question 41.
Which one of the following is not a transition element?
(A) Fe
(B) Co
(C) Ca
(D) Cr
Answer:
(C) Ca

Question 42.
The atomic number of an element is 19. In modern periodic table, this element is placed in :
(A) First period
(B) Second period
(C) third period
(D) fourth period
Answer:
(D) fourth period

Question 43.
The element, which has zero electron affinity is third period is :
(A) Al
(B) P
(C) Ar
(D) S
Answer:
(C) Ar

Fill in the blanks :

1. The cause of periodicity of elements in the periodic table is that these elements have _______ configuration.
Answer:
similar.

2. The radioactive element among halogens is _______.
Answer:
astatine.

3. AIl the lanthanides and actinides belong to ________ group in the periodic table.
Answer:
3 or IIIB.

4. Inert gases have the general electronic configuration ________.
Answer:
n s² sp}⁶

5. The elements of s and p-blocks are collectively known as _______ elements.
Answer:
representative

6. First I.P. of nitrogen is ______ than that of oxygen.
Answer:
greater.

7. \(\mathbf{N a}^{\oplus}\) ion is _______ in size than Na-atom.
Answer:
smaller.

8. Strong electropositive elements are ______ good.
Answer:
reducing agents.

9. Ca²⁺ has a smaller ionic radius than K⁺because it has ______.
Answer:
higher nuclear charge.

10. The ionisation potential of an element ________ on moving from left to right in a period.
Answer:
increases.

11. On Pauling’s electronegativity scale, the element next to F is ______.
Answer:
oxygen.

12. Transition metal compounds are coloured because of ______.
Answer:
absorption of visible light.

13. Elements of group IA are called ______ metals.
Answer:
alkali.

14. Electronegativity or non-metallic character gradually ______ along a period from left to right.
Answer:
increases.

15. In a period, all the elements have the same number of electronic ______.
Answer:
shells.

16. Atomic size refers to the distance between the centre of nucleus and the ______ shell of an atom.
Answer:
outermost.

17. The vertical columns in which elements of similar physical and chemical properties occur in the periodic table are called _______.
Answer: groups.

18. Atomic number of an element is more ______ than its atomic weight.
Answer:
fundamental.

19. The term ‘periodic’ means _______ of anything at regular intervals.
Answer:
recurrence.

20. The elements belonging to zero group are chemically _______
Answer:
inert.

21. Hydrogen belongs to the ______ period.
Answer:
1 A (one).

22. Helium belongs to the ______ group.
Answer:
0 (zero).

25. The periodic table is seen to be divided into different horizontal series called _______.
Answer:
periods.

24. The elements in the modern periodic table are arranged in the increasing order of their _______.
Answer:
atomic number.

25. There are _____ elements in the fourth period of the periodic table.
Answer:
18.

26. The energy released when electron is added to a neutral gaseous atom is called ______ of the atom.
Answer:
electron affinity

27. Second period of periodic table contains ________ elements.
Answer:
8

28. Halogens are strong ______ agents.
Answer:
Oxidant

29. Along a period from left to right atomic radii ________.
Answer:
decreases

30. Name of a transitional element.
Ans:
copper

31. Across a period the number of ______ electrons increases by 1, while down the group they remain same.
Answer:
valence

32. All inert gases except _______ has 8 electrons in their outermost shell.
Answer:
helium

33. The basis of modern periodic table is _______ number.
Answer:
atomic

34. According to the modern periodic law, ________ of elements are a periodic function of their atomic number.
Answer:
properties

35. Group 3 to 12 contains elements known as ________ elements.
Answer:
transition

36. On going down a group in the periodic table, the size of atoms _______.
Answer:
increases

37. The incomplete period in the periodic table is _______.
Answer:
7th period

38. If an element has low tonization energy, it is likely to be _______.
Answer:
metallic

39. The elements in ______ are called alkaline earth metals.
Answer:
Group-2

40. The elements in group1 are called _______ metals.
Answer:
alkali

State whether the following statement is True or False : VSA

1. Mendeleev’s eka-silicon was later found to be silicon.
Answer:
False

2. An element with three electron shells and two valence electrons belongs to third period and Group two.
Answer:
True

3. A metal “X” is in the first group of the periodic table. The formula of its oxide is X₂O.
Answer:
True

4. All the elements of a particular group in the periodic table have the same number of valence electrons.
Answer:
True

5. On moving from left to right in a period of the periodic table, the size of the atom increases.
Answer:
False

6. Group 17 elements are called rare earth elements.
Answer:
False

7. The modern periodic table was prepared by Niels Bohr.
Answer:
True

8. In Lothar Meyer’s atomic volume versus atomic mass curve, the peaks are occupied by the alkali metals.
Answer:
True

9. On moving from left to right in a period, the electropositive character of elements decreases, but electronegeative character increases.
Answer:
True

10. Lithium, Sodium and Potassium form a Dobereiner’s triad.
Answer:
True

11. Lother Meyer pointed out that atomic volumes of solid elements are periodic functions of their atomic weight.
Answer:
True

Comprehensive WBBSE Class 10 Physical Science Notes Chapter 3 Chemical Calculations can help students make connections between concepts.

Chemical Calculations Class 10 WBBSE Notes

Accuracy: It refers to how close a measurement is to the true value.

Precision : It refers to how close one measurement is to another.

Scientific notation: The measurements of quantities in chemistry are spread over a wide range of 10^-31 to 10⁺²³. Hence, a convenient system of expressing the numbers in scientific notation is used.

Types of chemical reactions:

• Combination: e.g. Fe + S → FeS
• Decomposition: e.g. 2 KClO₃ → 2 KCl + 3 O₂
• Double Decomposition: e.g. AgNO₃ + NaCl → AgCl + NaNO₃
• Rearrangement or Isomerisation: e.g NH₄ CNO → NH₂ CONH₂ (Urea)
• Displacement: e.g. Zn + CuSO₄ → ZnSO₄ + Cu
• Polymerisation: e.g. n(CH₂ = CH₂) →(-CH₂-CH₂-)_n
• Neutralisation: e.g. HCl(aq) + NaOH(aq) → NaCl(aq) + H₂ O
• Redox Reactions : e.g. H₂ S + Br₂ → 2 HBr + S
• Catalytic Reactions: e.g. N₂ + 3 H₂ \(\stackrel{\mathrm{Fe} / \mathrm{Mo}}{\rightleftharpoons}\) = 2 NH₃
• Plastic catalytic Reactions: Which require light as well as a catalyst to take place e.g. manufacture of starch and sugar by plants from CO₂ and H₂O in presence of light and chlorophyll (catalyst)

Laws of chemical combination:

• Law of conservation of Mass: (A. Lavoisier, 1774)
• Law of Definite proportions: (Louis Proust, 1799)
• Law of Multiple proportions: (John Dalton, 1804)
• Law of Reciprocal proporticns: (Richter, 1792)
• Gay Lussac’s Law of Gaseous volumes: (Gay Lussac, 1809)
• Dalton’s Atomic Theory: (John Dalton, 1803)

Atomic mass: It is the average relative mass of an atom of an element as compared to the mass of a carbon atom (12_c) taken as 12.

Atomic mass unit: It is the quantity of mass equal to \(\frac{1}{12}\) th of the mass of a carbon atom ( ¹²C). 1 amu = 1.6605 × 10^-24 g

Carbon atomic mass: It is the atomic mass of an element expressed in gram.

Kelation among atomic mass, equivalent weight and valency:

Atomic mass = Equivalent weight × Valency

Avogadro constant: The number of atoms or any other particles present in a given system is expressed in the terms of Avogadro constant. (6.022 × 10²³)

Molar volume: The volume of gaseous substance (element or compound) under a fixed temperature and pressure is known as volume of the gas.

Mole (SI system): A mole is the amount of substance which contains as many entities (atoms, molecules, ions or any other particle) as there are atoms in exactly 0.012 Kg (or 12 g) of the carbon -12 isotope.

Empirical formula: It is the formula of a compound which gives the simple whole number of ratio of the atoms of various elements present in one molecule of compound.

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.

Structural formula: A formula which gives the actual arrangement of the different atoms in the molecule are linked together is called a structural formula of the compound.

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.

Mass-mass relationship problems: In this type of problems mass of one of the reactants/products is to be calculated if that of the other reactants/products are given.

Limiting reactant: The reactant which is completely used and determines the amount of product formed is known as limiting reactant.

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.

Percent yield: Percent yield which is the ratio of the actual yield to the theoretical yield multiplied by 100.

Stoichiometry: The quantitative study of the reactants required or the products formed is called stoichiometry.

Dulong and Petit’s Law: It states that ‘the product of atomic weight and specific heat of an element is approximately equal to 6.4.

Isomorphism: Substances having same crystalline structure are said to isomorphous. e.g. ZnSO₄.7 H₂O and FeSO₄.7 H₂O

Vapour density: It is the ratio of the mass of a certain volume of the gas to the mass of same volume of hydrogen under similar conditions of temperature and pressure.

Relation between molecular weight and vapour density :
Molecular weight = 2 × Vapour density

Relation between empirical formula and molecular formula.
Molecular formula = n × Empirical formula
(n = a simple whole number and
may have values 1,2,3,…)

Equivalent weight: It is the number of parts of a substance which combine with or displace directly or indirectly 1.008 parts by weight of hydrogen or 8 parts by weight of oxygen or 35.5 parts by weight of chlorine.

Atomicity of a gas: It is the number of atoms present in one molecule of a gaseous element.

Solubility: The amount of solute in grams that can be dissolved in 100 grams of a solvent to form a saturated solution at a definite temperature is called the solubility.

Percentage by weight [%(w/w)]: It is the amount of solute in grams present in 100 grams of the solution.

Weight/volume percentage [%(w/v)]: It is the amount of solute in grams present in 100 mL of the solution.

Volume/volume percentage [%(v/v)]: It is the volume in mL of the solute percentage in 100 mL of the solution.

Normality (N): It is the number of gram equivalents of solite dissolved per litre of a solution.

Molarity (M): It is the number of moles of solute dissolved per litre of the solution.

Formality (F): It is the number of gram formula weight of the ionic solute dissolved per litre of the solution.

Molality (m): It is the number of moles of solute dissolved in 1000 g of the solvent.

Mole fraction: It is the ratio of the number of moles of one component to the total number of moles of substances in the solution.

Parts per million (ppm.): It is defined as the number of parts of a component per million parts of the solution.

The following equations are generally used for weight-weight calculation.

2 KClO₃ = 2 KCl + 3 O₂
Zn + H₂ SO₄ = ZnSO₄ + H₂
CaCO₃ = CaO + CO₂
2 NH₄ Cl + CaO = 2 NH₃ + CaCl₂ + H₂O
Mg + H₂ SO₄ = MgSO₄ + H₂
CaCO₃ + 2 HCl = CaCl₂ + H₂O + CO₂
2 H₂ + O₂ = 2 H₂O

Comprehensive WBBSE Class 10 Physical Science Notes Chapter 8.2 Ionic and Covalent Bonding can help students make connections between concepts.

Ionic and Covalent Bonding Class 10 WBBSE Notes

Chemical Bond: The chemical force that hold the atoms together in a molecule is called the Chemical Bond.

Cause of chemical bonding

1. Tendency to acquire noble gas configuration: From the electronic configuration of the noble gases it is clear that all noble gases (except helium) have eight electrons in their valence shell i.e. they have ns², np⁶configuration.

The noble gas configurations are highly stable and have no tendency to lose or gain electrons. Thus, inert nature of noble gases is due to their stable electronic configuration.

Atoms of all other elements do not have eight electrons in their valence shall (outermost orbit).
Therefore, atoms of these elements combine with other or with atoms of other elements to acquire stable configuration of the nearest noble gas (according to octet rule).

This tendency of atoms of various elements to acquire stable configuration of the nearest noble gas is the cause of chemical combination.

2. Tendency to acquire minimum energy: All systems tend to attain stability by lowering their potential energy. Increase in attractive forces leads to decrease in energy. Conversely, decrease in attractive force or increase in repulsive forces increases energy.

Let us now apply these principles to bonding between atoms. Even, atom bies to attain a state of minimum energy. When two atoms are brought closer to form a molecule, following forces come into play.

Attractive forces between electrons of one atom and nudeus of other. Repulsive forces due to inter-electronic and inter-molecular repulsive forces. The molecule becomes stable when there is a net increase in the attractive force. This Increase in attractive force results in decrease energy. Greater the decrease in energy, more stable the molecule will be.

• Electronic theory of valency: According to electronic theory (developed by Kosel and Lewis. 1916) the valency of on element is the number of electrons that its atoms can gain, lose or share to acquire stable nearest noble gas configuration.

Depending upon the mode of acquiring nearest noble gas configuration, there are three common types of bonds.

• Ionic or Electrovalnet bond
• Covalent bond
• Co-ordinate or Dative bond.

Apart from these chemical bonds, there are some physical bonds (which are electrosintic in nautre). The main types of physical bonds are:

• Hydrogen bond
• Metallic bond
• Vander Waai’s interactions

(a) ionic bonding :

The electrostatic force of attraction which holds the oppositely charged ions together is known as ionic bond or electrovalent bond and the compounds which are formed by the transference of electrons from one atom to the other are called ionic or electrovalent compounds. The number of electrons which an atom loses or gain while forming an ionic bond is known as its electrovalency.

Conditions necessary for the formation of ionic bond

• Formation of cation from a neutral atom having low ionisation energy.
• Formation of an anion from an anion from a neutral atom with high value of electron affinity.
• Formation of crystal lattice from oppositely charged ions involving large release of energy. Higher the Lattic energy of a crystal, more readily it will get formed.

Characteristics of Ionic Compounds:

• All ionic compounds are usually crystalline solids and are composed of ions even in the solid state.
• Ionic solid have high melting points and boiling points due to the presence of strong attractive forces between the oppositely charged ions.
• These are highly soluble in polar solvents (such as water) haveing high dielectric constant but insoluble in organic solvent (such as benzene, alcohol, ether etc.)
• Ionic compounds have low volatility, high density and high stability.
• In molten state or in solution in polar solvents, ionic compounds are good conductors of electricity.
• In solution, ionic compounds undergo ionic reactions which are very fost.
• Crystals of certain Ionic compounds have similar arrangement of atomns as well as geometry.
• Ionic bonds are non-directional and due to the non-directional nature of ionic bonds, ionic compounds do not show isomerism.
• Ionic compounds are hard and brittle

(b) Covalent Bond (Lewis Concept) :

A covalent bond is formed by the mutual sharing of electrons between the atoms, both of which are short of electrons. The compound so formed is called covalent compound. The number of electrons contributed by an atom for sharing is called its covalency. Depending upon the number of electrons shared between two atoms being one, two or three, we have single covalent bond ( : or -), double convalnt bond ( : : or = ) and triple convalent bond ( or ).

Characteristics of Covalent Compounds:

• Covalent compounds exist in solid, liquid or gaseous state.
• Covalent compounds like napthalene in which molecules are held together by weak Vander Waal’s forces, have low melting points and boling points.
• Covakrnt bonds are rigid and directional in nature.
• Covalent solids like diamond, Si, C etc. consisting of giant molecules are bad conductors of electricity due to the absence of free electrons or ions.
• Since i.e dissolves like, polar covalent compounds like sugar are soluble in polar solvents like water and the non-polar compounds like naphthalene are more soluble in non-polar solvents Like benzene.
• Covalent compounds are neither hard nor brittle like ionic compounds.
• Covalent compounds undergo molecular reactions in solution.

Examples of covalent compounds and their structures:

Factors affecting the formation of ionic bonds :

• The ionization energy of the electropositive element should be low i.e. the metal atoms form a low charged positive ion easily.
• The quantitative value of electron affinity of electronegative element should be high i.e. the non-metal atom is small and give rise to low charged negative ion easily.
• Lattice enthalpy should be high.

Lattice enthalpy : The energy given off when gaseous positive and negative ions together to form 1 mole of the solid ionic compound is called Lattice enthalpy (U)
Na⁺ (g) + Cl(g) → NaCl (s)    ΔH = -U
For the reverse process, NaCl (s) → Na⁺(g) + Ch(g)    ΔH = +U
Lattice enthalpy a charge of ions
Lattice enthalpy \(\alpha \frac{1}{\text { size of ions }}\)

Lattice enthalpy play an important role in deciding the solubility of ionic solids.

• If the anion and the cation are of comparable size, the cation radius will influence the lattice energy. Since lattice energy decreases much more than the hydration energy with increasing ionic size, solubility will increase as we go down the group.
• If the anion is large compared to cation, the lattice energy will remain almost constant within a particular group. Since, the hydration energies decrease down a group, solublity will decrease as found for alkaline earth metal carbonates and sulphates.
• Born-Haber cycle : The fundamental of this cycle is based upon the fact

Example :
According to Hesse’s law

Thus, lattice energy of Nacl(S) has a large negative value. This indicates that the compound is highly stable.
Finding the number of covalent bonds.

Finding the number of covalent bond electron shored
Number of covalnent bonds between two atoms = \(\frac{\text { electron shored }}{2}\)
Total number of shared electrons S = N – A

S = the total number of electrons shared in the molecule or polyatomic ion.
N the number of valence shell electrons needed by all the atoms in the molecule or ion to achive noble gas configuration [ N = 8x] number of atoms ( H excluded) + 2 x number of H-atoms]
A = the number of electrons available in the valnece shell of all of the representative atoms. This is equal to the sum of their periodic group number.
e.g. in CO₂ for 0-atom, A = 6 and for C-atom, A = 4
Thus A = 4+2 x 6 = 16
N = 8 x 3=24
S = 24 – 16 = 8
Thus, there are eight electrons shared to form bonds.
: Ö : : C : : Ö :
Formal charge: The atoms of a molecule or ion are usually neutral i.e. carry no charge for some purposes, such as to find reaction mechanism,assigning of formal charge of atoms in a molecule or ion is important.

• Favourable factors for covalent bonding (Fajan’s rule)

(i) The charge on cation or anion must be larger. The increased charge will increases the polarisation of the other ion (anion), thus covalent character is increased.

(ii) The cation must be smaller because in the fact, the charge possess will be more concentrated, thus causing more polarisation of anion. Hence we can say that ionic compounds having smaller cations show more covalent nature.

(iii) The anion must be larger. In such anions, the aoter electrons will be at a greater distance from the nucleus, hence more easily influenced by the attractive forces of cation. As the result larger anions will be more easily polarised in comparison to smaller anions.

(iv) The polarising power of those cations which donot have inert gas configuration will be more in comparision to cations having inert gas configuration.

• Some important covalent bond parameters :

(i) Bond length: The average distance between the centre of nuclei of the two bonded atoms in a molecule is known as bond length. It depends upon the size of atoms hybridization, steric effect, resonance etc.

(ii) Bond enthalpy: Bond enthalpy is the amount of energy required to break a particular bond in one mole of gaseous molecule.
Bond enthalpy α electronegative

(iii) Bond order : It is the number of covalent bonds present between the two atoms in a molecule.
order a bond enthalpya bond length
Bond order a bond enthalpy α \(\frac{1}{\text { bond length }}\)

(iv) Bond angles : It is the angle between the bonded orbitais. Generally it decreases, as the number of lone pair of electrons increases, or as the electronegativity of the central atom decreases.

However, in molecule having same central atom, bond angle increases as the electronegativity of surrounding atom decreases.

∴ The order of eledronegativity is CI > Br > I

• Type of covalent Bonds:

(i) Non-Polar Conalnt Bond : If the covalent bond is formed between two homonuclear atoms i.e. between atoms of exactly equal electronegativity, the electron pair is equally shared between them. Such a bond is called non-polar covalent bond, e.g. H₂, Cl₂, F₂  etc.

(ii) Polar covalent bond : If the bond forming entities are dissimilar i.e. heteronuclear or with different electronegativity, the bond formed has partial ionic character as the electron pair is attracted by more electronegative entity. Such a bond is called polar covalent bond.

The greater difference in electronegativity higher is the polar nature.

Electronegativity : The electronegativity of an element is the tendency or ability its atom to attract the bonding or shared pair of electrons towards itself in a covalent bond. The relative order of electro negativity of some important element is:

Electronegativity is maximum in : F (4.0)
Electronegativity is minimum in: Fr (0.7)

Co-ordinate bond:
A Co-ordinate bond is a special type of covalent bond in which the shared pair of electrons is contributed by one of the two combining atoms. A Co-ordinate bond is represented by an arrow ( – ) pointing from the donor towards the acceptor.
Example:

Characteristics of co-ordinate compounds :

• The compounds exhibit all three states i.e. solid, liquids and gases under ordinary conditions.
• The melting and boiling points of these compounds and higher as compared to covalent compounds but lower than those of ionic compounds.
• Like covalnent compounds these are also poor conduction of electricity in solid as well as fused state.
• These compounds are sparingly soluble in polar solvent like water, however, these are readily soluble in organic solvent.
• Compounds are generally as stable as covalent compounds. The addition compounds are not very stable.
• Co-ordinate linkage is rigid and directional, thus compounds exhibit isomerism.
• Cd-ordinate compounds show molecular reactions just like covalent compounds.
• The dielectric constants of these compounds are higher.

Dipole moment : The product of the magnitude of positive or negative charge (q) and the distance (d) between the centres of positive and negative charges in a polar molecule is called dipole moment.
μ = q x d (p = Dipole moment)

The unit of dipole moment in CGS system in debey and in SI system is Coulomb-metre.

Dipole moment is a vector quantity, thus indicated by the symbol (+→) pointing towards the negative end e.g.

For symmetrical molecules, dipole moment, dipole moment is zero but unsymmetrical molecules have some dipole moment e.g.

However symmetric molecules like HF, H₂O, NH₃, have some dipole moment

By using dipole moment, the precentage ionic character of a polar bond (A-B) is calculated as,

Resonance: The various Lewis structures, which differ in the positions of non-bonding or π-electrons but not in the relative positions of atoms are called resonance structures contributing structure or canonical forms and this concept is known as resonance.

Example : Benzene molecule can be represented as a resonance hybrid (III) of two kekule structures, (I) and (II).

\(\mathrm{BO}=\frac{\text { total number of bonds between two atoms in all the structures }}{\text { total number of canonical forms }}\)

The stability of a resonance structure can be decided by considering the following points-

• A non-polar canonical form is more stable.
• More the number of covalent bonds, more is the stability.
• Resonance structure in which negative charge resides on electronegative atom and positive charge on electropositive atom and positive charge on electropositive atom is more stable as compared to that for which opposite is true.
• Hydrogen bond The electrostatic force of attraction existing between the H-atom covalently bonded to an electronegative atom (F, O or N) in a molecule and the electronegative atom of another molecule (similar or different type) is known as hydrogen bond.

Types of hydrogen bonding

(i) Intermolecular hydrogen-onding : When hydrogen bonding occurs between different molecules of the same or different compounds, it is called intermolecular hydrogen bonding.
Example:

(ii) Intramolecular hydrogen bonding : When hydrogen bonding takes place within the same molecule, it is called intramolecular hydrogen bonding.
Examples :

• Hybridisation : It may be defined as the process of inter mixing of atomic orbitals of the same atom having same or slightly different energies so as to redistribute their energies and give new orbitals of equal energies and identical shapes.

• Types of hybridisation :

Determination of hybridisation of the central atom
H = \(\frac{1}{2} [V+X – C . A ]\)
H = Number of orbitals involved in hybridisation ;
V = Number of electrons in the valence shell of the central atom ;
X = Number of monovalent atoms surrounded the central atom ;
C = Change on cation.
A = Change of anion.

Difference between Electrovalent and Covalent Compounds :

Electrovalent Compound	Covalent Compound
1. These are formed by the transfer of one or more electrons from one atom to another. 2. These consist of ions. 3. These are soluble in water but insoluble in organic solvents. 4. These are hard solids with high melting and boiling points. 5. These conduct electricity in fused as well as aqueous solutions. 6. These undergo ionic reactions which are very fast. 7. These do not show isomerism.	1. These are formed by the sharing of one or more electrons between the bonded atoms. 2. These consist of invidual molecules. 3. These are isoluble in water but solute in organic solvents. 4. These exist as gases, liquids or soft solids with low melting and boiling points. 5. These do not conduct electricity. 6. These undergo molecular reactions which are very slow. 7. These show isomerism.