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.

Comprehensive WBBSE Class 10 Physical Science Notes Chapter 2 Behaviour of Gases can help students make connections between concepts.

Behaviour of Gases Class 10 WBBSE Notes

Matter: It is classified into three States: Solid, liquids and gases.

Some Physical properties of gases:

Motion of gas molecules: A gas is composed of infinite number of molecules. Molecules of gaseous substances move almost freely and exhibit random motion in all directions.

Shape and Volume: A gas has niether a definite shape nor a definite volume. It takes the shape and volume of the container in which it is kept.

Density: Gases have lower density than the liquids and solids.

Diffusion: When two or more gases which do not react with each other, are brought in contact, they intermix with one another forming a homogeneous mixture. This spontaneous mixing of gases with one another is known as diffusion.

Expansibility: Gases exhibit unlimited power of expansion.

Compressibility: The compressibility of a gas is very high.

Temperature of a gas: Temperature of any gas is the measure of average kinetic energy of the gas molecules.

Pressure of a gas: The force exerted by the gaseous molecules per unit area of the wall due to continuous collision of the gas molecules with the walls of the container is called the pressure of the gas.

• Unit of area: CGS unit : cm²
• SI unit : m²
• Unit of force: CGS unit : dyne
• SI unit : Newton

Unit of pressure:

• The pressure of gas is generally expressed in the unit of atmosphere (atm).
• Torr: Pressure exerted by exactly 1 mm of mercury column at 0°C and at standard gravity is termed as 1 torr.
• Bar: The commonly used unit of pressure = bar

1 atm = 1.01325 bar

Pascal (Pa) : SI unit of pressure is pascal. The pressure exerted when a force of 1 newton acts on 1 m² area is called 1 pascal.

1 atm = 76.0 cuHg = 760 mm Hg = 760 torr

psi : The pressure is also expressed in the unit of pound per square inch or psi.

1 atm = 14.7 psi

Measurement of pressure exerted by a gas : Very common instrument used for measuring the pressure of gas is manometer.

Pressure (P) = \(\frac{\text { Force }}{\text { Area }}\) = \(\frac{\mathrm{A} \times \mathrm{h} \times \mathrm{d} \times \mathrm{g}}{\mathrm{A}}\) = hdg

Unit of volume : At a particular temperature and pressure the volume of a gas closed in a container is equal to the volume of that container at the same temperature and pressure.

• Units : SI units of volume : m³
• Smaller units : dm³, cm³
• The symbol used for litre is : L
• The symbol used for millilitre is : mL

The relationship among different units are :

1 L = 10³ mL=10³ cm³=10³ ×(10^-1)³ dm³ = 1 dm³
1 m³=10⁶ cm³=10³ dm³=10³ L.

NTP or STP (Normal or Standard Temperature and Pressure): It is defined as the pressure exerted by column of mercury 76 cm in height at 0°C at 45° latitude and mean sea-level.

Boyle’s law (1662): At constant temperature, the volume of a given mass of a gas in inversely proportional to the pressure of the gas.

Mathematical expression of Boyle’s law: Let the pressure of a definite mass of a gas be P and the volume be V. If the temperature of T K (kelvin), then according to Boyle’s Law,

V ∝ \(\frac{1}{P}\)

when temperature T and the mast.
remain constant.
or, V = K.\(\frac{1}{P}\) when temperature T and the mass of the gas ‘m’ remain constant.
or, V = K.\(\frac{1}{P}\) (K = Proportionality Constant)
∴ PV = K, this equation is the mathematical expression of Boyle’s law.

Graphical representation of Boyle’s Law :

At constant temperature plot of P vs. V for a definite mass of gas.

At constant temperature plot of P V vs. P for a definite mass of gas.

At constant temperature plot of \(\frac{I}{V}\) vs. P and V vs. \(\frac{1}{P}\) for a definite mass of gas

At constant temperature plot of log P vs. log V for a definite mass of gas

Isotherms: These are the pressure volume curves obtained at constant temperature.

Charle’s Law (1787): At constant pressure, the volume of a given mass of a gas increases or decreases by \(\frac{1}{273}\) of its volume at 0° C for each one degree rise or fall in temperature.

Mathematical expression of Charle’s law :

(V₀ = Volume of a given mass of gas at Constant pressure at 0°C
V_t = Volume of the gas after t°C rise of temperature)

Absolute zero : According to Charle’s law: At constant pressure, the temperature (-273°C) at which, theoretically a gas would have no volume, is known as absolute zero. A temperature below this cannot be conceived of in the universe.

Absolute scale of temperature : It is a thermometric scale where -273°C is the starting point i.e. on this scale 0 K is equal of -273° C and each degree is equal to that in the celsius scale.

Alternative Statement of Charle’s law : The volume of a given mass of a gas is directly proportional to the absolute temperature if the pressure remains constant.

Mathematical expression of Charle’s law with respect to absolute temperature.

V ∝ T at constant pressure and a definite mass of gas.
or, V = KT
or, [\(\frac{V}{T}\) = K = const

Graphical representation of Charle’s law

At constant pressure, plot of \(\frac{V}{1}\) vs. T for a definite mass of gas.

At constant pressure plot of V vs. t°C for vs. T for a definite mass of gas. definite mass of gas plot of V vs. t°C

At constant pressure plot of log V vs. log T for a definite mass of gas.

Graphical representation of P vs T at constant volume and for a definite mass of gas- According to Gay-Lussac’s law.

Combined form of Boyle’s and Charle’s law :
Let us consider for a definite mass of a gas the pressure, temperature and volume are P, T and V respectively.

According to Boyle’s Law

V ∝ \(\frac{1}{P}\) (at constant temperature and for a given mass of the gas)
According to Charle’s law
V ∝ T (at constant pressure and for a given mass of the gas)
According to the laws of joint variation,
V ∝ \(\frac{T}{P}\) when the mass of the gas remains constant but both pressure and temperature of the gas vary.
∴ V = K.\(\frac{T}{P}\)

(K = proportionality constant and it depends upon the amount of gas)
or, PV = KT
This equation is the combined form of Boyle’s law and Charle’s law.

Ideal gas: A gas which obeys Boyle’s law, Charle’s law and Avogadro’s law for all volumes of temperature and pressures and which obeys the equation of state P V=n R T under all conditions of temperature and pressure is called an ideal gas.

Real gases: The gases which do not obey PV=n R T equation are called real gases.

The compressibility factor (Z)
\(\left(Z=\frac{P V}{n R T}\right)\) of an ideal gas = 1

All gases approach the ideal behaviour as the temperature goes further from their boiling points i.e. at high temperature and low pressure.

Gay-Lussac’s Law: Under the same conditions of temperature and pressure two or more gases combine chemically in simple ratios by volumes of and the volumes of the products if gaseous also bear a simple relation to the volumes of the reacting gases.

Berzelius hypothesis: Under the same conditions of temperature and pressure equal volumes of all gases contain the same number of atoms.

Avogadro’s Law: Under the same conditions of temperature and pressure, equal volumes of all gases (element or compound) contain the same number of molecules.

Avogadro’s Number: Avogadro’s number may be defined as the number of molecules present in one gram-mole of any substance, element or compound (solid, liquid or gas).
N = 6.022 × 10²³, R.A. Millikan determined the value by oil drop experiment in 1913.

Molar volume: The volume occupied by one gram-molecule of any gaseous substance (elementary or compound) at a fixed temperature and pressure is known as the molar volume.
At standard conditions of temperature and pressure (STP), the volume equal to 22.4 litres is the molar volume of all gases.

Substance	Molecular mass
H2O	2 × 1 + 16 = 18
N2	14 × 2 = 18
O2	16 × 2 = 32

Pressure of dry gas = Atmospheric pressure – Aqueous tension

Equation of state for an ideal gas :
According to Boyle’s law, V ∝ \(\frac{1}{P}\) (T and n are constant)
According to Charle’s law, V ∝ T (P and n are constant)
According to Avogadro’s law, V ∝ n (P and T are constant)
By method of compound variation
V ∝ \(\frac{n T}{P}\) when P, T and n of the gas vary
or V = \(\frac{R n T}{P}\) (R = molar gas constant )
or, PV = nRT
This equation is called ideal gas equation.

Calculation of molar mass from equation of state

PV = nRT
[Let the mass of the gas = wg
Molecular mass of the gas = M

Dimension of Molar gas constant R

R = energy K^-1 mol^-1

Values of R in different units

Unit	Volume of R
L-atm	0.0821 L–atm mol -1K-1
Cal 1	1.987 Cal-1 K-1
SI	8.314 J mol-1 K-1
CGS	8.314 × 107 erg-1 mol-1 K-1
Dm3.torr	62.36 dm3 .torr. mol -1 K-1
Dm3.kPa	8.314 dm3.Pa.mol-1 K-1

Boltzmann constant (K)

Determination of density and molar mass of an ideal gas : For n moles ideal gas, the equation of state is :

PV = nRT, n = \(\frac{m}{\bar{M}}\)

(If ‘m’ and ‘M’ are the mass of the gas in gram and molar mass of the gas respectively, then the number of moles of gas n = \(\frac{m}{\bar{M}}\))

The above equation indicates the relation among the density, pressure, absolute temperature and moiar mass of an ideal gas.

Dalton’s law of partial pressure: At constant temperature, when two or more non-reacting gases are er:closed together in a container of definite volume, the total pressure of a mixture of gases is equal to the sum of the partial pressures of the constituent gases.

P_Total= P₁ + P₂ + P₃ +…

Diffusion of gas: The process of the property by virtue of which two or more gases without any external help intermix with each other spontaneously to form a homogeneous gas mixture irrespective of their densities or molar masses is termed as diffusion of gas.

Effusion: The process of out-flow of a gas confined in a closed vessel under high pressure through a fine orifice (hole) made in the well of the vessel is called effusion.

Graham’s Law of diffusion: At constant temperature and pressure, the rate of diffusion of any gas in inversely proportional to the square root of its density.

\(r ∝ [latex]\frac{1}{\sqrt{d}}\) or, r = \(\frac{K}{\sqrt{d}}\)

(r = the rate of diffusion or effusion of gas,
d = the density of gas, K = proportionality constant)

Postulates of kinetic theory of gases:

• All gases consist of very large number of tiny particles called molecules that are in constant rapid motion.
• The gas molecules are perfectly round, very hard and separated by large distances. Their actual volume is thus, negligible as compared to the total volume of the gas.
• The gas molecules collide with one another and with the walls of the container. The pressure exerted by a gas is due to the bombardment of its molecules on the walls of the vessel.
• The collisions between the gas molecules are perfectly elastic, i.e. there is no loss of energy during these collisions.
• The distance between the gas molecules being very large, there is no effective force of attraction or repulsion between them.
• The gas molecules move freely in all directions. Their speed and direction change continuously due to collisions among them. As a result, their motion becomes zig-zag or random.
• The average kinetic energy of the gas molecules is directly proportional to the absolute temperature of the gas.

Influenre of pressure on volume occupied by a gas; effect of temperature on the spond of gas molecules and on the pressure exerted by the gas:

• If the velocities of the molecules increase, the magnitude of pressure increases and if velocities of them decrease, pressure decreases.
• The motion of gas molecules depends on temperature of the gas. If the temperature is increased, the velocity of the gas molecules or the kinetic energy of the gas molecules increases.

Deviation from Ideal behaviour :

The modified equation put forward by Vander Waals’ for one mole of a real gas as:

\(\left(P+\frac{a}{V^2}\right)\) (V-b) = RT

and for ‘n’ moles of the gas it is expressed as

\(\left(P+\frac{a n^2}{V^2}\right)\) (V-nb) = nRT

where ‘a’ and ‘b’ are constants called Vander Waals’ constants. The values of constants ‘a’ and ‘b’ depend upon the nature of the gas.

Comprehensive WBBSE Class 10 Physical Science Notes Chapter 8.3 Electricity and Chemical Reactions can help students make connections between concepts.

Electricity and Chemical Reactions Class 10 WBBSE Notes

Electrochemistry: The branch of chemistry which deals with the relationship between chemical energy and electrical energy and how one can be converted into another.

Conductors: A substance which allows the electric current to flow through it is known as a conductor, e.g. Cu, Ag, Au etc.

Non-conductors: A substance which does not allow the electric current to flow through it is known as non-conductors.

Type of conductors :
(i) (a) Metallic conductors e.g. Cu, Ag, Au etc.
(b) Non-metallic conductors e.g. graphite (carbon)
(ii) Electrolytes

(a) Metallic conductors: These are the substances (metals) which allow the current to pass through them but do not undergo any change in themselves.

(b) Electrolytes: Compounds which in the fused state or in aqueous solution can conduct electricity and are decomposed chemically yielding new substances are known as electrolytes.

Non-electrolytes: Compounds which in the fused state or in aqueous solution do not conduct electricity are known as non-electrolytes, e.g. pure water, alcohol, acetone, sugar, urea etc.

Electrolytes: It is the process of chemical decomposition of an electrolyte in solution or in the fused state by the passage of electric current.

Electrodes: Two conducting metal plates or graphite strips or rods, placed in a voltameter to pass electric current through the electrolyte during electrolysis are called electrodes.

Anode: The electrode through which current enters into the voltameter is connected to the positive terminal of a battery is called anode.

Cathode: The electrode, which is connected to the negative terminal of the battery is called the cathode.

Voltameter: The complete set up or vessel consisting of two metal plates and electrolytes in which electolysis takes place is called Voltameter.

Ions: For the passage of electricity, electrolytes are decomposed reversibly into charged particles. These charged particles are called ions.

Cation: The positively charged particles are migrated towards cathode and is called cation
e.g. H⁺, Na⁺, NH₄⁺ etc.

Anion: The negatively charged particles migrated towards anode is called anion,
e.g. Cl^–, SO₄^2-, NO₃^– etc.

Difference between Metallic conduction and Electrolytic conduction

Metallic conduction	Electrolytic conduction
1. Flow of electricity is due to the movement of electrons only and there is no movement of matter. 2. Flow of electricity takes place without the decomposition of the substance. 3. The electrical conduction decreases with increase of temperature.	1. Flow of electricity is due to the movement of ions and hence there is transfer of matter. 2. Row of electricity is accompanied by the decomposition of the substance (electrolyte). 3. The electrical conduction increases with increase of temperature.

Strong electrolytes : Those electrolytes which are ionised almost completely in the fused state or in aquous solution, are known as strong electrolytes, e.g. NaOH, NaCl, HCl, H₂SO₄

• Weak electrolytes : Those electrolytes which are ionised a little are called weak electrolytes
e.g. HCN, NH₄OH, CH₂COOH etc.

Difference between Atom and Ion :

Atom	Ion
1.  Atom is a neutral, smallest and active particle of element. Number of electrons and protons are same in atom.	1. Number of protons are not equal with number of electrons in ion.
2. Atoms do not exist in free state.	2. Ions exist in free state.
3. Chemically atoms are more reactive.	3. Ions are not reactive.

Electrolysis of some electrolytes:

Electrolysis of water:
Voltameter : Two platinum plates are introduced through a rubber cock attached in the bottom of glass vessel.
Electrodes : Two platinum plates.
Electrolyte : Water acidified with a few drop of dilute H₂SO₄.
Procedure : Two hard glass tube are filled with water. They are inverted over the two electrodes. When electric current is passed through the electrodes from a battery into the acidified water, electrolysis takes place. Gases (hydrogen and oxygen) are collected in the tube by the downward displacement of water.
It shows from experiment that gas collected in anode is oxygen and that collected in cathode is hydrogen.

Electrolytic reaction:

(iii) Reaction in cathode : H⁺+e → H; H + H → H₂↑
(iv) Reaction in anode : OH^– – e → OH ; 4OH → 2H₂O + O₂↑
Conclusion: In the electrolysis of water, it is found that at the same tem­perature and pressure one volume of oxygen (O₂) and two volumes of hydrogen (H₂) are evolved.

2. [Electrolysis of sulphuric acid
(a) Electrolysis of dilute sulphuric acid :
Electrodes: Two platinum plates

• Electrolytic reaction :

(b) Electrolysis of conc. H₂SO₄ (60%):

Conclusion : In the electrolysis of conc. H₂SO₄ (60%) it is found that at low temperature hydrogen gas is evolved at cathode and H₂O₂ is produced at anode.

3. Electrolysis NaCl
(a) Electrolysis of fused NaCl :
Electrodes :
Cathode — Platinum
Anode — Graphite

Electrolytic reaction :
(i) Decomposition of NaCl : NaCl \(\rightleftharpoons\) Na⁺ + Cl^–
(ii) Reaction in Cathode : Na⁺ + e \(\rightleftharpoons\) Na
(iii) Reaction in anode : Cl^– – e → Cl; Cl + Cl → Cl₂↑

Conclusion: In the electrolysis of fused NaCl It is found that sodium is produced at cathode and chlorine is evolved at anode.

(b) Electrolysis of dilute aqueous solution of NaCl :
Electrodes :
Cathode — Platinum
Anode — Platinum

Electrolytic Reaction:
(i) Dissolution of NaCl : NaCl \(\rightleftharpoons\) Na⁺ + Cla^–
(ii) Dissolution of water : H₂O \(\rightleftharpoons\) H⁺ + OH^–
(iii) Reaction in cathode : H⁺ + e → H; H + H → H₂↑
(iv) Reaction in anode : OH^– – e → OH; 4OH → 2H₂O + O↑

Conclusion : In the electrolysis of dilute aqueous solution of NaCl it is found that hydrogen is evolved at cathode and oxygen is produced at anode.

Electrolysis of cone aqueous solution of NaCl:

Electrodes :
Cathode — Graphite
Anode — Graphite

Electrolytic reaction :
(i) Dissolution of NaCl : NaCl \(\rightleftharpoons\)  Na⁺ + Cl^–
(ii) Dissolution of water : H₂O \(\rightleftharpoons\) H⁺ + OH^–
(iii) Reaction in Cathode : H⁺ + e → H; H + H → H₂↑
(iv) Reaction in Anode : Cl^– – e → Cl ; Cl + Cl → Cl₂↑
(v) Part of Cl₂ produced at anode reacts with NaOH;
2NaOH + Cl₂ = NaCl + NaOCl + H₂O (which is produced in solution)

4. Electrolysis of aqueous solution of copper sulphate :
(a) Using platinum electrodes :

Electrodes :
Cathode — Platinum
Anode — Platinum

Voltameter : An iron pot is used for electrolysis.
Electrolyte : Aqueous solution of copper sulphate

Electrolytic reaction:
(i) Dissolution of CuSO₄ : CuSO₄ \(\rightleftharpoons\)Cu²⁺+ SO₄²
(ii) Dissolution of water : \(\rightleftharpoons\) H⁺ + OH^– – Cu²⁺ + 2e
(iii) Reaction in cathode : Cu²⁺ + SO₄²
(iv) Reaction in anode : OH^– – e → OH; 4OH → 2H₂O + O₂↑

Conclusion : In the electrolysis of aqueous solution of copper sulphate using platinum electrodes, it is found that copper is deposited at cathode and oxygen is evolved at anode and the final solution becomes acidic due to the formation of sulphuric acid (H₂SO₄).

(b) Using copper electrodes :
Electrodes :
Cathode – Copper
Anode – Copper

Voltameter : An iron pot is used for electrolysis.
Electrolyte : Aqueous solution of copper sulphate

Electrolytic reaction:
(i) Dissolution of CuSO₄ : CuSO₄ \(\rightleftharpoons\) Cu²⁺ + SO₄^2-
(ii) n resolution of water : H₂O \(\rightleftharpoons\) H⁺ + OH^–
(iii) Reaction in cathode : Cu²⁺ + 2e → Cu^–
(iv) Reaction in anode : Cu – 2e → Cu²⁺

Conclusion : As a result of the electrolytic reaction describe above, anode is gradually dissoluted and due to deposition of copper in cathode it becomes thicker.

5. Electrolysis of aqueous solution of AgNO₃ :
(a) Using platinum electrodes:
Electrodes:
Cathode – Platinum

Anode – Platinum

Electrolyte : Aqueous solution of AgNO₃

Electrolytic reaction:
(i) Dissolution of AgNO₃ : AgNO₃ \(\rightleftharpoons\) Ag⁺ + NOg^–₃
(ii) Dissolution of water : H₂O \(\rightleftharpoons\) H⁺ + OH^–
(iii) Reaction in cathode : Ag⁺ + e → Ag
(iv) Reaction in anode : OH^– – e → OH; 4OH → 2H₂O + O₂↑

(b) Using silver electrodes :

Electrodes :
Cathode – Silver
Anode – Silver
Electrolyte : Aqueous solution of AgNO₃

Electrolytic reaction:
(i) Dissolution of AgNO₃ : AgNO₃ \(\rightleftharpoons\) Ag⁺ + NO^–₃
(ii) Dissolution of water : H₂O \(\rightleftharpoons\) H⁺ + OH^–
(iii) Reaction in cathode : Ag⁺ + e → Ag
(iv) Reaction in anode : Ag – e → Ag⁺

Practical application of electrolysis :

(i) Extraction of metal : Highly electro positive such as Na, Ca, Mg, Al etc. : metals are extracted by electrolysis method. e.g. Extraction of Aluminium (Al)

Electrolyte : It contains of pure alumina (Al₂O₃)-20% ;
Fused cryolite (Na₃A/F₆)-60% ; CaF₂-20%.

Electrolytic reaction:
(i) Decomposition of cryolite :
(Na₃AlF₆>) A1F₃ ; 3NaF \(\rightleftharpoons\)A1F₃+ 3NaF; A/F₃\(\rightleftharpoons\) Al³⁺ + 3F^–
(ii) Reaction in cathode : Al³⁺ + 3e → Al
(iii) Reaction in anode : 3F^– – 3e → 3F
(iv) Final reaction ; AF₂O₃ + 6F → 2A1F₃ + 3O ; 6O → 3O₂↑
Non-metals like oxygen, hydrogen, chlorine and industrial preparations of caustic soda (NaOH) and heavy water (D₂O) are done by electrolysis.

Electro-plating: Some metals are required to be electroplated because some­times for the preservation of the less active metal or article and to prevent rusting or for attractive appearance.

Electroplating of Cu, Ag. Ni, Sn, Cr, Zn, Au :

(iv) Metals after extraction by chemical means are purified by electrolysis, e.g. Purification of copper :

Electrolyte : In aqueous solution of copper sulphate, small amount of 1% H₂SO₄ is added to increase the conductivity of the solution.

Electrodes . Cathode : Pure thin copper plate Anode : Thick impure copper plate

Procedure : Electric current is now passed in the solution from a battery, copper ion is formed from anode and is mixed into the solution where in cathode copper metal is deposited.

Electrolytic reaction:

• Reaction in cathode : Cu²⁺ + 2e → Cu
• Reaction in anode : Cu – 2e → Cu²⁺

Conclusion : After passing electricity for sometimes it is found that anode, an impure copper metal is totally dissolved and a very thin plate of cathode gradually becomes thicker.

Ability to discharge ions in increasing order :

Comprehensive WBBSE Class 10 Physical Science Notes Chapter 5 Light can help students make connections between concepts.

Light Class 10 WBBSE Notes

Reflection of light: Light travelling in one medium when falls on a second medium, a portion of the incident light, depending on the nature of the surface of the second medium, is turned back into the first medium. This phenomenon is known as reflection of light.

Laws of reflection:

• The incident ray, the reflected ray and the normal at the point of incidence on the reflecting surface line in one plane.
• The angle of incidence is equal to the angle of reflection.

Real Image and Virtual image: If rays diverging from a point source after reflection or refraction suffer changes or direction and either actually converge to, or appear to diverge from a second point, the second point is called the image of the first point and the image is real in the first case and virtual in the second case.

Characteristics of the image formed by plane mirror

• the image is virtual
• the image is erect
• the size of the image is equal to the size of the object
• the image is formed as for behind the mirror as the object is infront of it
• the image is laterally inverted.

Effect of rotation of a plane mirror on the reflected ray: For a given incident ray, if a mirror be rotated through angle say θ, the reflected ray rotates through double the angle (2θ).

Multiple images formed by two mirrors inclined at an angle: When an object is kept between two mirrors inclined at an angle θ, a number of images are formed due to multiple reflections.

The number of images formed = \(\left(\frac{2 \pi}{\theta}-1\right)\)
when θ = 90°, images formed 3.
when θ = 0°, images formed infinite.

Spherical mirrors: A spherical mirror is a reflecting surface so curved that it forms a part of a regular hollow sphere.

Centre of Curvature: The centre of the sphere of which the mirror is a part is called the centre of curvature of the mirror. C and C’ are the centres of curvatures of a concave and a convex mirror respectively.

Radius of curvature: The radius of the sphere of which the mirror is a part called its radius of curvature (r).

Aperture: The perimeter of a spherical mirror is generally circular in shape and diameter (AB) of this circle is called aperture of the mirror.

Pole: The central point (P) of the mirror is called its pole.

Principal axis: The straight line (XX’) passing through the pole and centre of curvature is called principal axis of the mirror.

Principal section: When a spherical mirror is intersected by a plane passing through the principal axis, the section is a circular arc (APB) called principal section of the mirror.

Principal focus: A beam of rays parallel to the principal axis of a spherical mirror after reflection either converges to (in case of a concave mirror) or appears to diverge from (in the case of a convex mirror) a fixed point (F) on the axis, which is called the Principal focus of the mirror.

Focal length: The distance of the focus from the pole of the mirror is called the focal length (PF) of the mirror.

Focal plane: The plane passing through the principal focus of a mirror and at right angle to its principal axis is called the focal plane of the mirror.

Sign conventions:

As the radius of curvature and focal length of a concave mirror are measured towards the left of its pole, so they are taken as negative in the new cartesian sign convention.

As the radius of curvature and focal length of a convex mirror are measured towards the right of its pole, so they are taken as positive in this sign convention.

Relation between radius of curvature and focal length

r = 2f

The mirror formula: The general equation for a spherical mirror is

\(\frac{1}{u}+\frac{1}{v}=\frac{2}{r}=\frac{1}{f}\)

Linear magnification: The ratio of the linear size of the image to the linear size of the object is called the linear magnification.

m = \(\frac{h2}{h1}\) = \(\frac{-v}{u}\)

This relation is valid for both the mirrors (concave and convex).

In the case of a concave mirror depending on the position of the object, the image may be real, inverted, magnified, of same size or diminished and also virtual erect and magnified.

In the case of a convex mirror the image is always virtual, erect and diminished for all positions of the object.

The relation between the speed of object and fmage formed by a spherical mirror:

v_i = speed of image
v_o = speed of object

Applications of spherical mirrors:

• A concave mirror is used as a shaving mirror as it produces magnified erect image.
• A concave mirror is used as a reflector in search lights, head lights in cars, solar cookers etc.
• A concave mirror is used by the opticians in opthalmoscopes for reflecting light on the retina.
• A convex mirror is used as rear view mirrors, in automobiles as it always produces an erect image of diminished size giving a wide field of view.
• A convex mirror is used as a reflector in street lamps, as it can diverge light over a large area.

Refraction of light: The phenomenon of change in the direction of light ray, when it passes obliquely from one homogeneous medium to another is called refraction of light.

Laws of refraction:

The incident ray, the refracted ray and the normal at the point of incidence on the refracting surface lie in the same plane.

Snell’s Law: For a given pair of media and for a given colour of light, the sine of the angle of incidence bears a constant ratio to the sine of angle of refraction.

\(\frac{\sin t}{\sin r}\) = const = μ₂ (refractive index)

Types of refractive index :

Absolute refractive index: The refractive index of a medium with respect to vacuum or air is taken as the absolute refractive index of the medium.

Relative refractive index: The refractive index of a medium with respect to any other medium is called its relative refractive index.

Principle of Reversibility of Light: The principle states that if the path of ray of light is reversed after so suffering a number of reflections and refractions, it retraces its path. Thus according to this principle, image and object positions can be interchanged. The points corresponding to object and image are called conjugate points.

Generalised Snell’s law of refraction:

μ₁ sin i = μ₂ sin r

Optically denser media: When the absolute refractive index of a medium is greater then that of a second medium, then the first medium is called the optically denser media than the second one.

Optically rarer media: The second medium is called optically rarer media.

Real depth and Apparent depth:

When μ₁>μ₂, real depth > apparent depth i.e. when the observer is in rarer medium the image appears closer to the surface than the object.

When μ₂ = 1 i.e. when the observer in the air medium, μ₁= μ = refractive index of the medium in which object is situated then

μ = \(\frac{\text { real depth }}{\text { apparent depth }}\)

When μ₂>μ₁ i.e. when the observer in the denser medium, the image appears further away from the surface than the object.

For this reason a tank filled with water or any transparent liquid appears less deep. Also a straight stick put obliquely in water appears bent. lens is called double convex lens. It is used in camera, telescope etc.

Refraction through a parallel slab:

\({ }_1 \mu_2 \times{ }_2 \mu_1=1\)

Refraction through a compound slab:

\({ }_1 \mu_2 \times{ }_2 \mu_3={ }_1 \mu_3\)

Total internal reflection : It is a phenomenon in which a ray of light travelling from an optically denser medium to an optically rarer medium is incident at an angle greater than the critical angle for the pair of media in contact, the ray is totally reflected back into denser medium.

Conditions for total internal reflection :

• light must travel from a denser to a rerer medium.
• angle of incidence in the denser medium must be greater than the critical angle for the pair of media in contact.

Relation between refractive index and critical angle :

sin i_c = \(\frac{1}{μ}\)

Spherical refracting surface: A refracting surface, which is a part of a sphere of transparent refracting material is known as a spherical refracting surface.

Types of spherical refracting surfaces :

• convex spherical refracting surface: These surface have convex towards rarer medium side.
• Concave spherical refracting surface: These surfaces have towards rarer medium side.

Refraction from rarer to denser medium at a convex spherical refracting surface:

Image formation by a concave mirror:

Position of the object	Position of the image	Size of the image	Nature of the image
between	Behind the	Enlarged	virtual and erect
P and F	mirror	Highly enlarged	Real and inverted
A + F	A + infinity	Enlarged	Real and inverted
Between	Beyond C	Same size	Real and inverted
C and F	A + C	Diminished	Real and inverted
A + C	Between F and C	Highly dminished point sized	Real and inverted
Beyond C	At the focus F	Size of the image	Nature of the image
A + infinity	Position of the image	Enlarged	virtual and erect

Image formation by a convex mirror:

Position of the object	Position of the image	Size of the image	Nature of the image
At infinity	At the focus F, behind the mirror	Highly diminished point	virtual and erect
Between infinity and the pole P of the	Between P and F behind the mirror	sized	virtual and erect

The new cartesian sign convention for spherical mirrors :

Absolute Refractive index of some material media:

Lenses: A lens is a portion of a transparent medium bounded by two polished surfaces with at least one of them being curved.

Types of Lenses: Lenses are broadly of two types :

• Convex lens: If the lens is thicker at its centre than at its edges, it is a convex lens.
• Concave lens: The lens which is thinner of the centre and wider at the two edges is called a concave lens.

Other types of lenses:

Double convex lens : If both the surfaces of convex lens are convex then the lens is called double convex lens. It is used in camera, telescope etc.

Plano-convex lens: If one surface of convex lens is plane and the other is cinvex then it is called plano convex lens. It is used in eye piece of telescope.

Concavo-convex lens: If one surface of convex lens is convex and the other is concave then it is called concavo convex lens. It is used in spectacles.

Double-concave lens: It both the surfaces of concave lens are concave then the lens is called double concave lens.

Plano-concave lens: If one surface of concave lens is plane and the other is concave then if is called plano-concave lens.

Convexo-concave lens: If one surface of concave lens is concave and the other is convex then if is called convexo-concave lens.

Focal plane of lens: The plane passing through principal focus of a lens and perpendicular to the principal axis of the lens is known as the focal plane of the lens.

Centre of curvature: The spherical surface of a lens is a part of sphere. The centre of the sphere is known as centre of curvature of the surface of lens.

Principal axis of a convex lens: The line joining the centres of curvature of the two spherical surfaces of a convex lens is called its principal axis.

Redius of curvature: Radius of curvature of a lens is the radius of the glass sphere from which the surfaces of the lens are cut.

Focus of convex lens : It a beam of parallel rays, travelling parallel to the principal axis of a convex lens are refracted by the lens, the rays became converging and intersect each other at a particular point on the axis. The point is known as the focus of the convex lens.

Optical centre: It a ray of light strikes one surface of a lens in such a way that emergent ray from the other surface is parallel to it, then the corresponding, refracted ray passed through a definite point on the principal axis. The point is the optical centre of the lens.

Focal length: The distance between the optical centre and the focus is known as focal length.

Formation of image by a lens:

• A ray parallel to the principal axis would pass through the second focus in case of a convex lens or appear to diverge from the second focus in case of a concave lens.
• A ray passes through optical centre of the lens undeviated.
• A ray actually passing through the first focus in case of convex lens or appearing to diverge from the first focus in case of concave lens comes out of the lens parallel to the principal axis.

Location of images formed for both types of lenses in different cases:

Object placed in infinity, the image is real, inverted, diminished and formed at the focus in the focal plane (fig. 5.8)

In (fig 5.9) is shown the position of image formed by a convex lens due to an object between 2 f and the infinity. The image is formed in between f and 2 f and real, inverted and diminished.

The situation for an object at a distance of 2 f is shown in (fig 5.10). The image is real, inverted of equal is size to the object and formed at a distance of 2 f from the lens.

In (fig 5.11) is shown the position of the image formed by a convex lens when the object lies between 2 f and f. The image is real, inverted and magnified.

In (fig 5.12) is shown when the object is situated at the focus of the convex lens. The image is real, inverted, highly magnified and is situated at infinity.

In (fig 5.13) is shown when the object is situated at a position less than the focal length of the convex lens. The image is erect virtual and magnified.

It can be shown in the case of a concave lens image is always erect, diminished and virtual [fig(g).]. As the object from infinity towards the lens, the image moves from the focus towards the lens.

Human eye: Human eye can be treated as a natural optical camera. It is nearly spherical in shape having following principal parts.

• Cornea
• Iris
• Pupil
• Lens
• Retina
• Ciliary muscles
• Optic nerve.

Working of eye :

The working of eye is similar to that of a Camera. In eye the amount of light entering it is adjusted by the iris, like the shutter in camera. The size of the opening of the pupil is changed by ciliary muscles. In a camera focussing of image is done by moving the lens forward or backward, while in human eye its focal length is changed by changing its shape by muscular effort.

The eye lens which is a convex lens forms a real, inverted image on the retina of the eye. The retina contains cells of the shape of rods and cones, which convert light energy into electrical signals and carried to brain through optic nerves. These signals are interpreted by the brain and we are able to see the object.

Accomodation of eye : The process by which ciliary muscles change the focal length of the eye lens so that a sharp image of the object at any distance from the eye is formed on the retina is called accomodation of eye.

Range of normal eye : The range of a normal eye varies from 25 cm to infinity.

Near point : The nearest point from an eye at which an object can be placed to see its sharp image is near point. (25 cm).

Far point: The farthest point from an eye at which an object can be placed to see its sharp image is called far point. For a normal eye the far point is infinity from the eye.

Power of accomodation : For a normal eye, the power of accomodation is about 4D (dioptre).

Defects of vision and their corrections : The common defects of human eye are –

Myopia (short-sightedness) : The defect where far point is less than infinity is known as myopia.
For correction of a myopia eye a concave lens of focal length-d is to be used. The power p of the lens is given by \(\frac{100}{f(\mathrm{in} \mathrm{cm})}\) dioptre.

Hypermetropia.(Long-sightedness): The defect where the near point moves away from 25 cm, but the eye can see distant objects without difficulty is called hypermetropia.

The defect can be corrected by using a convex lens of suitable focal length. Power of the lens \(\frac{100}{f(\text { in } \mathrm{cm})}\) dioptre

Presbyopia : The defect where an eye cannot see the near objects as well as distant objects clearly is called presbyopia.
To correct this defect bifocal lens of proper power and type is used with the lower one a convex lens to correct the near point and upper one a concave lens to correct the far point.

Astigmatism : The defect where an eye cannot focus horizontal and vertical lines simultaneously is known as astigmatism.
The cause of this defect is that the cornea of the eye has different curvatures in different directions.
Astigmatism is corrected by using a cylin-drical lens of suitable radius of curvature and suitable axis.

Prism: A prism is a portion of a transparent medium bounded by at least two plane faces inclined at suitable angle to each other.

Refraction through a prism

Angle of the prism

A = r₁ + r₂

Deviation produced

D = i₁ + i₂ – A

Minimum deviation : It is seen that the angle of deviation depends upon –

• angle of incidence
• angle of the prism
• Nature of the material of the prism

Dispersion of light : The phenomenon of splitting of a beam of white light into its constitutent colours is called dispersion of light.

Spectrum : The band of different colours obtained due to dispersion of white lens is known as a spectrum.

Cauchy’s formula : D = (μ-1) A

A prism only splite up the colours already present in white light and does not produce the colours.
The splitting of colours takes place at the first refracting surface of the prism only. In the second surface it is further refracted.
As all colours travel in vacuum with same speed, the material of the prism has same m for all the colours and so no dispersion takes place in vacuum.
The dispersion phenomenon is not exhibited by sound waves in air.
Scattering of light : The process of radiating light by atoms and molecules of the medium in all directions is called scattering of light.

Lord Rayleigh’s equation :

a = \(\frac{A V}{r \lambda^2}\)

\(I_s \propto \frac{1}{\lambda 4}\)

(a = amplitude of scattered light at a distance r from the scattering particle in V volume. A = the amplitude of incident light of wave length λ.)

The intensity of scattered light varies inversely as the fourth power of the wavelength of the incident light-provided the size of the particles scattering light of very very small as compared to the wavelength of the incident light.

Some phenomena due to scattering of light

Blue colour of sky: \(I_s \propto \frac{1}{\lambda 4}\)

The intensity of the scattered blue light would be much more than that of the red colour. Thus in a clear sky, blue colour becomes prominent colour and the sky appears blue.

The clouds appear white

Reddish appearance of sun at sunrise and sunset.

Danger signals are red.

Pure spectrum: The spectrum in which the constituent coloums do not overlap an each other and are separated distinctly into elementary colours in known as a pure spectrum.

Impure spectrum: The spectrum in which the constituent colours partially superpose an each other and are not separated distinctly into elementary colours is known as impure spectrum.

Well structured WBBSE Class 10 Physical Science MCQ Questions Chapter 8.6 Organic Chemistry can serve as a valuable review tool before exams.

Organic Chemistry Class 10 WBBSE MCQ Questions

Question 1.
C_nH_{2n + 2} is general formula of ________
(A) Alkenes
(B) Alkynes
(C) Alkanes
(D) Ring
Answer:
(C) Alkanes

Question 2.
Aliphatic hydrocarbons with double bond : ________
(A) are saturated
(B) generally add bromine
(C) belong to the acetylene family group
(D) belong to the paraffin
Answer:
(B) generally add bromine

Question3.
When sodium acetate is heated with soda lime, the reaction is called: ________
(A) Dehydration
(B) Decarboxylation
(C) Dehydrogenation
(D) Dehydrohalogenation
Answer:
(B) Decarboxylation

Question 4.
Ethylene can be prepared by reacting ethyl bromide with : ________
(A) Alcoholic KOH
(B) Amoniacal AgNO₃
(C) Acidified KMnO₄
(D) C and H₂SO₄
Answer:
(A) Alcoholic KOH

Question 5.
The product obtained when chloroform is treated with silver powder is: ________
Ethylene
ethane
Acetylene
Methane
Answer:
Acetylene

Question 6.
A metallic carbide on treatment with water gives a colourless gas which burns readily in air and gives a precipitate with ammoniacal silver nitrate. The gas is : ________
(A) Methane
(B) Ethane
(C) Ethylene
(D) Acetylene
Answer:
(D) Acetylene

Question 7.
A gas decolourises bromine in CCl₂ and forms a precipitate with ammoniacal silver nitrate. The gas is :
(A) Acetylene
(B) Ethylene
(C) Methane
(D) Ethane
Answer:
(B) Ethylene

Question 8.
The LHCC bond angle in ethylene is : ________
(A) 90°
(B) 120°
(C) 109° 28’
(D) 180°
Answer:
(B) 120°

Question 9.
Saturated hydrocarbons mainly undergo : ________
(A) Addition reactions
(B) Substitution reactions
(C) Elimination reaction
(D) Polymerisation
Answer:
(B) Substitution reactions

Question 10
Which of the following bonds is strongest?

Answer:
(C)

Question 11.
The reaction
is called : ________
(A) Kolbe’s reaction
(B) Annizzaro’s reaction
(C) Sabatier and Senderen’s reaction
(D) Clemmensen reaction
Answer:
(C) Sabatier and senderen’s reaction

Question 12.
Both methane and ethane may be obtained in one step reaction from ________
(A) C₂H₄
(B) CH₃I
(C) CH₃OH
(D) C₂H₅OH
Answer:
(B) CH₃I

Question 13.
Which of the following liberates methane on treatment with water ?
(A) Silicon carbide
(B) Calcium carbide
(C) Aluminium carbide
(D) Iron carbide
Answer:
(C) Aluminium carbide

Question 14.
On heating sodium acetate with sodium hydroxide, the gas evolved will be : ________
(A) Acetylene
(B) Ethane
(C) Methane
(D) Ethylene
Answer:
(C) Methane

Question 15.
A compound having a triple bond is more reactive because : ________
(A) there is a strain in the molecule
(B) valency of hydrogen is different
(C) electron density is higher
(D) none
Answer:
(C) electron density is higher.

Question 16.
Acidic hydrogen is present in : ________
(A) Ethyne
(B) Ehene
(C) Benzene
(D) Ethane
Answer:
(A) Ethyne

Question 17.
Final product of the oxidation of hydrocarbon is : ________
(A) CO₂ and H₂O
(B) Alcohol
(C) Acid
(D) Aldehyde
Answer:
(A) CO₂ and H₂O

Question 18.
General formula for alkenes is : ________
(A) C_nH_2n
(B) C_nH_2n+1
(C) C_nH_2n-1
(D) C_2nH_2n
Answer:
(A) C_nH_2n

Question 19.
Marsh gas mainly contains : ________
(A) H₂S
(B) CO
(C) CH₄
(D) C₂H₂
Answer:
(C) CH₄

Question 20.
Which of the following gases is used in welding ?
(A) C₂H₄
(B) C₂H₂
(C) CH₄
(D) C₂H₆
Answer:
(B) C₂H₂

Question 21.
Which hydrocarbon is used in making printer’s ink and paints ?
(A) CH₄
(B) C₂H₆
(C)  C₂H₄
(D)  C₂H₂
Answer:
(A) CH₄

Question 22.
The sugar which is stored in the liver to act as reserve food is : ________
(A) Glycogen
(B) Glucose
(C) Sucrose
(D) Fructose
Answer:
(A) Glycogen

Question 23.
Sweetest among all the sugar is : ________
(A) Fructose
(B) Glucose
(C) Sucrose
(D) Lactose
Answer:
(A) Fructose

Question 24.
The main structural feature of protein is : ________
(A) Ether linkage
(B) Peptide linkage
(C) Ester linkage
(D) All the above
Answer:
(B) Peptide linkage

Question 25.
Which of the following is protein ?
(A) Terry cotton
(B) Natural silk
(C) Nylon
(D) Rayon
Answer:
(B) Natural silk.

Question 26.
Which of the following contains nitrogen ?
(A) Fats
(B) Proteins
(C) Carbohydrate
(D) None
Answer:
(B) Proteins

Question 27.
Which of the following is an organic compound ?
(A) urea
(B) NaHCO₃
(C) CO₄
(D) NH₄ CNS
Answer:
(A) urea

Question 28.
Organic compound are:________
(A) high melting
(B) low meffing
(C) soluble in water
(D) conducts electricity in molten state
Answer:
(B) low melting

Question 29.
Tetravalence of carbon is proposed by: ________
(A) Wohler
(B) Lavoisier
(C) Kekule
(D) Vant Hoff
Answer:
(C) Kekule

Question 30.
Tetrahedral model of carbon compounds proposed by: ________
(A) Kekule
(B) Rutherford
(C) Wohier
(D) Vant Hoff
Answer:
(D) Vont Hoff

Question 31.
The number of covalent bonds present in ethane is : ________
(A) 4
(B) 6
(C) 7
(D) 9
Answer:
(C) 7

Question 32.
Which molecule has tetrahedral geometry? ________
(A) methane
(B) ethylene
(C) acetylene
(D) carbon dioxide
Answer:
(A) methane

Question 33.
Which does not react with metallic sodium?
(A) methyl alcohol
(B) ethyl alcohol
(C) acetic acid
(D) dimethyl ether
Answer:
(D) Dmethyt ether

Question 34.
How many positional isomers are possible with the molecular formula C₃H₁₀?
(A) 1
(B) 2
(C) 3
(D) 4
Answer:
(C) 2

Question 35.
How many functional isomers are possible with molecular formula C₃H₈O?
(A) 1
(B) 3
(C) 2
(D) 4
Answer:
(C) 2

Question 36.
IUPAC name of CH₃ CH₂ CH₂ OH is:
(A) propan-1-oI
(B) n-propanol
(C) isopropanol
(D) propyl alcohol
Answer:
(A) Propon-I-ol

Question 37.
IUPAC name of Formaldehyde Is:
(A) Butanal
(B) Propanal
(C) Ethanal
(D) Methanal
Answer:
(D) Methanal

Question 38.
The total number of different carbon chains that five carbon atoms form in alkane is:
(A) 5
(B) 4
(C) 3
(D) 2
Answer:
(C) 3

Question 39.
The IUPAC name of the hydrocarbon present in rectified spirit is :
(A) methanol
(B) ethanol
(C) trichioromethane
(D) ethanai
Answer:
(B) ethanol

Question 40.
Which of the following functional group is present in vinegar?
(A) -CHO
(B) C=O
(C) -COOH
(D) -OH
Answer:
(C) -COOH

Question 41.
Which of the following can damage optic nerve?
(A) acetic acid
(B) ethyl alcohol
(C) acetone
(D) methanol
Answer:
(D) methanol

Question 42.
Which one of the following is not a polymer?
(A) LPG
(B) Jute
(C) PVC
(D) PET
Answer:
(A) LPG

Question 43.
Urea was synthesized by wohier from ………
(A) ammonia and carbon monoxide
(B) ammonium cyanate
(C) ammonium thiocyanate
(D) ammonium chloride and CO₂
Answer:
(B) ammonium cyanate

Question 44.
Identify the wrong statement
(A) Organic compounds have low m.p. and b.p.
(B) Organic Compounds are Soluble in solvent having high dielectric constant.
(C) Most organic compounds are do not conduct electricity
(D) Most of the organic compounds are liquid or gaseous under ordinary temperature and pressure.
Answer:
(b) Organic Compounds are soluble in solvent having high dielectric constant.

Question 45.
Organic compounds are generally
(A) Soluble in water
(B) insoluble in water
(C) ionize in water
(D) hydrolyze in water
Answer:
(B) insoluble in water

Question 46.
The biggest source of methane is …………….
(A) Synthesis gas
(B) natural gas
(C) nerve gas
(D) LPG
Answer:
(B) natural gas

Question 47.
Chlorine reacts with saturated hydrocarbons at room temperature in the
(A) presence of sunlight
(B) absence of sunlight
(C) presence of moisture
(D) presence of an acid catalyst
Answer:
(A) presence of sunlight

Fill in the Blanks:

1. …………. is the abbreviation of polyvinyl chloride.
Answer:
PVC.

2. The monomer of …………. is tetrafluoroethene.
Answer:
teflon.

3. …………. is a large molecule made up of many similar units of small molecules.
Answer:
Polymer.

4. The compound bearing the monovalent functional group – CHO are ………….
Answer:
aldehydes.

5. Alkynes are hydrocarbons where at least two carbon atoms combine with a …………. bond.
Answer:
triple.

6. The function group of organic acid is ………….
Answer:
– COOH

7. The functional group of …………. is -NH.
Answer:
amines.

8. Hydrocarbons in which at least two carbon atoms join with a double bond are called ………….
Answer:
alkenes.

9. Catenation is the property where a large number of …………. atoms link together to form large organic molecules.
Answer:
carbon.

10. Proteins contain various kinds of …………. acids.
Answer:
amino

11. RNA is the abbreviation for…………. acid.
Answer:
ribonucleic.

12. …………. is a complex organic compound responsible for reproduction and maintaining heredity.
Answer:
Gene.

13. …………. and proteins are the polymerisation products of amino acids.
Answer:
Polypeptides.

14. Amino acids are the end products of the digestion of ………….
Answer:
proteins.

15. Polypeptide chains are the chains of ………….
Answer:
polymers of amino acids.

16. Sucrose on hydrolysis give one …………. and one fructose molecule.
Answer:
glucose.

17. Starch is …………. saccharide.
Answer:
poly.

18. Carbohydrates containing a keto group are called ………….
Answer:
ketoses.

19. Vitamin C is soluble in ………….
Answer:
water.

20. Globular proteins me …………. in water.
Answer:
soluble.

21. The carbon chains in alkenes are ………….
Answer: zig-zag.

22. Hydrocarbons are more soluble in …………. solvents.
Answer:
non-polar.

23. Ethane on combustion produces ………….
Answer:
Carbon dioxide and water.

24. AlC evolves …………. when treated with water.
Answer:
methane.

25. Halogenation of alkanes does not occur in ………………….
Answer: dark.

26. Wurtz reaction is used for the preparation of ………………….
Answer:
alkanes.

27. Melting point of organic compounds are …………………. than of inorganiccompounds.
Answer:
lower.

28. Organic compounds are …………………. and inorganic compounds are…………………..
Answer:
covalent, electrovalent

29. Kekule proposed C is …………………. and Vant Hoff proves C is ………………….
Answer:
tetravalent, covalent

30. The simplest alkane is …………………..
Answer:
methane

31………………… is the active ingredient of all alcoholic drinks.
Answer:
Ethanol

32. The first organic compound synthesized in the laboratory is ……..
Answer:
urea

33. H – C – H bond angle is methane is …………….
Answer:
109°28′

34. The existence of huge number of carbon compounds are due to two properties of carbon : tetravalency and ……………
Answer: catenation

35. n-propyl alcohol and iso-propyl alcohol exhibit…………… isomerism.
Answer:
positional

36. Methane, ethane and propane are the first three members of a ………….. series.
Answer:
homologous

37. …………. is the main constituent of CNG.
Answer:
Methane

38. Ethanoic acid is commonly known as…………..acid.
Answer:
acetic

39. IUPAC name of formic acid is …………
Answer:
methanoic acid

State whether the following statement is True or False : VSA

1. One must not drive a car after consuming alcohol._________________
Answer:
True

2. Denatured spirit cannot be consumed orally._____________________
Answer:
True

3. ‘Carbon’ comes from the Latin word ‘carbo’ meaning coal.
Answer:
True

4. Methane is the main constituent of marsh gas.
Answer:
True

5. Industrially ethane is produced by catalytic cracking of petroleum.
Answer:
True

6. Burning of methane in air is an exothermic reaction.
Answer:
True

7. PVC is highly fire resistant,
Answer:
True

8. Ethanol is used as a solvent in laboratory.
Answer:
True

9. Ethanol damages the optic nerve and may cause blindness.
Answer:
False

10. Teflon is hydrophobic and high heat resistant.
Answer:
True

Well structured WBBSE Class 10 Physical Science MCQ Questions Chapter 6 Current Electricity can serve as a valuable review tool before exams.

Current Electricity Class 10 WBBSE MCQ Questions

Multiple Choice Questions :

Question 1.
The SI unit of electric charge is:
(A) Coulomb
(B) Ampere
(C) Ohm
Answer:
((A) Coulomb

Question 2.
The unit of potential difference is :
(A) joule
(B) volt
(C) ohm
(E) ampere
Answer:
(B) volt

Question 3.
The unit of electrical power is:
(A) volt
(B) watt
(C) ohm
(D) joule
Answer:
(B) wait

Question 4.
What material an electric fuse made of?
(A) copper
(B) silver
(C) iron
(D) tin-lead alloy
Answer:
(D) Tintead alloy

Question 5.
Unit of resistance is:
(A) ampere
(B) ohm
(C) coulomb
(D) joule
Answer:
(B) ohm

Question 6.
Specific resistance of a conductor dipends on :
(A) its length
(B) its cross-sectional area
(C) its material
Answer:
(C) its nateriat

Question 7.
The amount of heat developed due to current can be known from:
(A) Ampere’s law
(B) Ohm’s law
(C) Joules law
Answer:
(C) Joules lau

Question 8.
The example of conservation of electrical energy into mechanical energy is:
(A) electric cell
(B) electric motor
(C) electric lamp
Answer:
(B) electric motor

Question 9.
The action of electric current on magnet was first observed by:
(A) Oerested
(B) Joule
(C) Barlow
(D) Newton
Answer:
(A) Oerested

Question 10.
Ohm’s law is related to:
(A) current and potential difference
(B) volume and pressure
(C) temperature density.
Answer:
(A) current and potenitial difference

Question 11.
Electric supply company measures the electricity consumed by the consumers in their household in terms of :
(A) joule unit
(B) watt-hour
(C) B.O.T. units
Answer:
(C) B.OT inits

Question 12.
Which one is not conductor of electricity:
(A) copper
(B) gold
(C) aluminium
(D) plastic
Answer:
(D) plastic

Question 13.
Ammeter measures:
(A) resistance
(B) potential difference
(C) current
Answer:
(C) current

Question 14.
Potential difference is measured by:
(A) Voltmeter
(B) Volameter
(C) Galvanometer
Answer:
(A) Voltmeter

Question 15.
If the length of the conductor is kept unaltered and cross section of conductor is increased then its resistance:
(A) increases
(B) decreases
(C) remains unaltered
Answer:
(B) decreases

Question 16.
If the corss section of the conductor is kept unaltered and length of conductor is increased then its resistance:
(A) increases
(B) decreases
(C) remains unaltered
Answer:
(A) increases

Question 17.
The correct relation is :
(A) Watt = \(\frac{\text { Volt }}{\text { Ampere }}\)
(B) Watt = \(\frac{\text { Ampere }}{\text { Volt }}\)
(C) Watt = Volt × Ampere
Answer:
(C) Watt = Volt × Ampere

Question 18.
The physical quantity measured by kilowatt-hour
(A) Electric power
(B) Electric energy
(C) Current
Answer:
(B) Electric energy

Question 19.
What is the equivalent resistance of the resistances 2 ohm, 3 ohm and 5 ohm combined in parallel ?
(A) 10 ohm
(B) \(\frac{30}{31}\) ohm
(C) \(\frac{31}{30}\) ohm
(D) 20 ohm
Answer:
(B) \(\frac{30}{31}\) ohm

Question 20.
What is the equivalnnt resistance of the resistances 3 ohm, 5 ohm and 12 ohm combined in series?
(A) 15 ohm
(B) 18 ohm
(C) 20 ohm
(D) 30 ohm
Answer:
(C) 20 ohm

Question 21.
Force between two charges separated by a certain distance in air is F. If each charge was doubled and distance between them also doubled, then force would be
(A) F
(B) 2 F
(C) 4 F
(D) F / 4
Answer:
(A) F

Question 22.
What is the dimensional formula of electric charge ?
(A) [M⁰ L⁰ TA]
(B) [M⁰ L⁰ T^-1 A]
(C) [M⁰ L⁰ TA^-1]
(D) [M⁰ L⁰ T^-1 A^-1]
Answer:
(A) [M⁰ L⁰ TA]

Question 23.
A charge q₁ exerts some force on a second charge q₂. If a hird charge q₃ be brought near, the force of q₁ exerted on q₂.
(A) decreases
(B) increases
(C) remains unchanged
(D) increases if q₃ is of same sign as q}₁ and decreases of q₃ is of opposite sign.
Answer:
The force between q₁ and q₂ is not affected by q₃.

Question 24.
The dimensional formula of electric density is
(A) MLT^-2 A^-1
(B) MLT^-3 A^-1
(C) ML² T^-3 A^-1
(D) ML² T^-3 A_-2
Answer:
(A) MLT^-3 A^-1

Question 25.
Electric flux at a point in an electric field is:
(A) positive
(B) negative
(C) zero
(D) none of these
Answer:
(C) zero

Question 26.
A soap bubble is charged to a potential of 16 V. Its radius is the doubled. The potential of the bubble now will be :
(A) 16 V
(B) 8 V
(C) 4 V
(D) 2 V
Answer:
(B) 8 V

Question 27.
A resistor of 0.5 Ω is connected to another resistor is parallel combination to get an equivalent resistance of 0.1 Ω. The resistance of second resistor is :
(A) 1/8 Ω
(B) 0.2 Ω
(C) 0.6 Ω
(D) 8 Ω
Answer:
(A) 1/8Ω

Question 28.
If six identical cells are each having emf of 6 V are connected in parallel the emf of the combination is :
(A) 1 V
(B) 1 / 6V
(C) 6 V
(D) 36 V
Answer:
(C) 6 V

Question 29.
The resistance of discharge tube is :
(A) ohmic
(B) non-ohmic
(C) both
(D) sometimes ohmic, sometimes non-ohmic.
Answer:
(B) non-ohmic.

Question 30.
A wire of resistance 1 W is stretched to double its length. The resistance will become
(A) 1/4
(B) 1
(C) 2
(D) 4
Answer:
(D) 4

Question 31.
A car battery has emf 12 V and internal resistance 5 × 10^-2 W. If it draws 60 A current, the terminal voltage of the battery will be
(A) 3 V
(B) 5 V
(C) 9 V
(D) 15 V
Answer:
(C) 9 V

Question 32.
The specific resistance of a wire depends upon :
(A) length
(B) cross sectional area
(C) mass
(D) none of these
Answer:
(D) None of these.

Question 33.
What is the unit for specific resistivity?
(A) Ohm-cm^-2
(B) Ohm-cm¹
(C) Ohm-cm
(D) Ohm-cm^-2
Answer:
(C) Ohm-cm

Question 34.
A battery having emf 4 V and internal resistance 0.5 W is connected with a resistance of 4.5 W, then the voltage at the terminals of battery is :
(A) 4.5 V
(B) 3.6 V
(C) 0 V
(D) 2 V
Answer:
(B) 3.6 V

Question 35.
The unit of specific conductivity is:
(A) ohm-cm^-1
(B) ohm-cm^-2
(C) ohm^-1-cm^-1
(D) ohm^-1 cm^-2
Answer:
(C) ohm^-1 cm^-1

Question 36.
The length of a wire is doubled. Its conductance will be :
(A) unchanged
(B) halved
(C) doubled
(D) quadrupled
Answer:
(B) halved.

Question 37.
Practical unit of resistance is ohm is equal to :
(A) 10⁹ emu
(B) 10⁷ emu
(C) 10¹¹ emu
(D) 10¹³ emu
Answer:
(A) 10⁹ emu

Question 38.
How many electrons constitute current of IA?
(A) 6.25 × 10⁹
(B) 6.25 × 10¹⁸
(C) 6.25 × 10⁵
(D) 6.25 × 10⁶
Answer:
(B) 6.25 × 10¹⁸

Question 39.
The resistance will be least in a wire with dimension
(A) L/2,2 A
(B) 2L, A
(C) L, A
(D) none of these
Answer:
(A) L/2,2A.

Question 40.
A cell of negligible resistance and emf 2V is connected to series combination of 2,3 and 5 ohm. The potential difference in vol across the 3 W resistance will be
(A) 6 V
(B) 3 V
(C) 2 / 3 V
(D) 0.6 V
Answer:
0.6 V

Question 41.
The material of a wire of a potentiometer is :
(A) copper
(B) steel
(C) manganin
(D) aluminium
Answer:
(C) magnanin.

Question 42.
Kirchhoff’s current law obeys conservation of :
(A) charge
(B) momentum
(C) energy
(D) none of these
Answer:
(A) charge.

Question 43.
Potentlometer measures potential more accurately because :
(A) It uses sensitive galvanometer for null deflection.
(B) It uses high resistance potentiometer wire.
(C) It measures the potential in the closed circuit.
(D) It measures the potential in the open circuit.
Answer:
(A) It uses sensitive galvanometer for null deflection.

Question 44.
A current loop placed in a magnetic field behaves like a:
(A) Magnetic dipole
(B) Magneitc substance
(C) Magnetic pole
(D) All are true
Answer:
(A) Magnetic dipole.

Question 45.
A charge + q is moving upwards vertically. It enters a magnetic field directed to the north. The force on the charged will be towards
(A) North
(B) South
(C) West
(D) East
Answer:
(C) West.

Question 46.
The vertical component of earth’s magnetic field is zero at a place where angle of dip is :
(A) 0°
(B) 45°
(C) 60°
(D) 90°
Answer:
(A) 0°

Question 47.
A magnetic needle suspended freely orients itself :
(A) in a definite direction
(B) in no direction
(C) upward
(D) downward
Answer:
(A) in a definite direction.

Question 48.
A material when placed in a magnetic field is thrown out of it. Then the material is :
(A) paramagnetic
(B) diamagnetic
(C) ferromagnetic
(D) non-magnetic.
Answer:
(B) diamagnetic.

Question 49.
Which of the following is an Ohmic resistance?
(A) diode value
(B) junction diode
(C) carbon-arc lamp
(D) nichrome
Answer:
(D) nichrome

Question 50.
For which of the following substances, resistance decreases with increase in temperature?
(A) copper
(B) mercury
(C) carbon
(D) platinum
Answer:
(C) carbon

Question 51.
In parallel combination of resistances –
(A) p.d. is same across each resistance
(B) total resistance is increased
(C) current is same in each resistance
(D) all of these are true
Answer:
(A) p.d. is same across each resistance

Question 52.
The main fuse is connected in :
(A) live wire
(B) neutral wire
C) both the live and earth wires
(D) both earth and neutral wire
Answer:
(A) live wire

Question 53.
The electric meter in a house records :
(A) charge
(B) current
(C) energy
(D) power
Answer:
(C) energy

Question 54.
When two negative charges are placed close together then :
(A) they attract each other
(B) they repel each other
(C) they become positive
(D) none of the above
Answer:
(B) they repel each other

Question 55.
If a source of EMF is traversed from negative to positive terminal, the potential change is :
(A) negative
(B) positive
(C) zero
(D) both negative\positive
Answer:
(B) positive

Question 56.
When the distance between the two charges are halved, the electrical force between the charges
(A) doubles
(B) reduces to one fourth
(C) halves
(D) quadraples
Answer:
(D) quadraples

Question 57.
Mercury behaves as a superconductor
(A) below 4.2K
(B) above 6.9 K
(C) below 23 K
(D) above 9.6 K
Answer:
(A) below 4-2 K

Question 58.
When a cell is in use, its emf E and terminal voltage v are related as :
(A) E = V
(B) E < V
(C) E > V
(D) none of these
Answer:
(C) E > V

Question 59.
Which one of the following behaves as a superconductor?
(A) platinum above 273 K
(B) mercury below 4.2K
(C) gold below -191°C
(D) fullerene at room temperature
Answer:
(B) mercury below 4.2K

Question 60.
If one of the resistors in a parallel circuit is removed, the total resistance will be :
(A) double
(B) same
(C) increased
(D) constant
Answer:
(C) increased

Question 61.
The flow of current in a circuit due to short circuit :
(A) reduces
(C) increases rapidly to dangerous level
(B) remains unchanged
(D) increases gradually
Answer:
(C) increases rapidly to dangerous level

Question 62.
If unit of I is ampere, unit of R is ohm, unit of t is second, then unit of H} is :
(A) Joule
(B) watt
(C) dyne / cm²
(D) ohm^-1
Answer:
(A) Joule

Question 63.
The relation between H, I, R and t is :
(A) H = I² R/t
(B) H/t = I²R
(C) R = I² t/H
(D) I² = HR/t
Answer:
(B) H/t = l² R

Question 64.
The filament of an incandescent bulb is ma e up of :
(A) tungsten
(B) aluminium
(C) copper
(D) nichrome
Answer:
(A) tungsten

Question 65.
Which of the following properties is not suitable for a fuse wire?
(A) low melting point
(B) high resistance
(C) thick and short in length
(D) thin and short in length
Answer:
(C) thick and short in length

Question 66.
The commercial unit of electrical energy we use is :
(A) wh
(B) kwh
(C) kw
(D) kilowatt.second
Answer:
(B) kwh

Question 67.
If an electrical appliance has E E R = 3.1, it is rated as :
(A) 2 star
(B) 3 star
(C) 4 star
(D) 5 star
Answer:
(D) 5 star

Question 68.
The electric meter in a house records
(A) energy
(B) current
(C) power
(D) charge
Answer:
(A) energy

Question 69.
Which one among the following is most energy efficient ?
(A) CFL
(B) tube light
(C) LED
(D) Incandescent lamp
Answer:
(C) LED

Question 70.
In a parallel circuit of bulbs
(A) same current exists in all the bulbs
(B) voltage across each bulb remains the same
(C) failure of any bulb leads to a break in the circuit
(D) All the above
Answer:
(B) voltage across each bulb remains the same

Question 71.
A current carrying conductor produces
(A) electric field
(B) magnetic field
(C) both
(D) none of these
Answer:
(B) magnetic field

Question 72.
A split ring in motion is called :
(A) armature
(B) rotor
(C) core
(D) commutator
Answer:
(d) commutator

Question 73.
The direction of an induced current can be predicted by :
(A) Ampere’s swimming rule
(B) Fleming’s left hand rule
(C) Fleming’s right hand rule
(D) Right-hand thumb rule
Answer:
(C) Fleming’s right hand rule

Question 74.
The frequency of alternating current supplied in India is :
(A) OHz
(B) 50 Hz
(C) 110 Hz
(D) 220 Hz
Answer:
(B) 50 Hz

Question 75.
Lenz’s law supports the principle of conservation of :
(A) mass
(B) energy
(C) momentum
(D) charge
Answer:
(B) energy

Question 76.
In commercial alternators, the rotor consists of
(A) armature coil
(B) brushes
(C) field magnets
(D) none of these
Answer:
(C) field magnets

Question 77.
The commercial generation frequency in India is :
(A) 50 Hz
(B) 60 Hz
(C) 100 Hz
(D) 150 Hz
Answer:
(A) 50 Hz

Question 78.
DC generators are also called :
(A) dynamo
(B) inverter
(C) storage cell
(D) alternator
Answer:
(D) alternator

Question 79.
The potential difference between the live wire and the neutral wire in domestic circuit is :
(A) 220 V
(B) 11 KV
(C) 33 KV
(D) 132 KV
Answer:
(A) 220 V

Question 80.
A switch must be connected in
(A) neutral wire
(B) live wire
(C) earth wire
(D) either live wire or neutral wire
Answer:
(B) live wire

Question 81.
Which of the two wires of a household ctrcuit are at the same potential?
(A) Live and Neutral
(B) Live & Earth
(C) Neutral and Earth
(D) None of them
Answer:
(C) Neutral and Earth

Fill in the blanks :

1. Coulomb = _____ × second.
Answer:
ampere

2. The equivalent resistance is smaller than the resistance in a parallel combination of _____ resistances.
Answer:
smallest

3. Potential difference = current × ______.
Answer:
resistance

4. 1² rt is some electrical _____.
Answer:
work

5. Power = potential difference × ______.
Answer:
current

6. Resistance of a wire is _____ proportional to the length of the wire.
Answer:
directly

7. A _____ is used to measure the potential difference between two points in a section of an electrical circuit.
Answer:
voltmeter

8. An ammeter is used to measure the _____ flowing through an electric circuit where the ammeter is connected in series.
Answer:
current

9. Short circuit occurs due to accidental direct contact of the live and the _____ wires.
Answer:
neutral

10. The total resistance of a number of resistors in series is equal to the ______ of the resistances of the component resistors.
Answer:
sum

11. Elecctomotive force is some _____ not a force.
Answer:
energy

12. In current electricity, the potential difference between two points is measured by the work done when unit _____ flows from one point to the other.
Answer:
charge

13. Potential difference between two points one _____ when work done to carry one coulomb charge between the points be 1 Joule.
Answer:
volt.

14. Resistance is the natural property of every material body by virtue of which the body _____ flow of electric charges through it.
Answer:
opposes

15. The current flowing through a conductor is directly proportional to the potential difference between its ends when _____ and other physical conditions of the conductor remain unaltered.
Answer:
temperature

16. Ohm’s law is not valid for current flowing through _____ under low pressure, electrolytes and semi-conductors.
Answer:
gases

17. If an electrical instrument of power 1 watt works for 1 hour, the electrical energy expended is known as 1 _____.
Answer:
watt-hour

18. Number of B.O.T. unit = \(\frac{\text { amphere } \times \text { volt }}{1000}\) × _____.
Answer:
hour

19. When electric current does not change the direction it is called _____.
Answer:
Direct Current.

20. Watt = Volt × _______.
Answer:
Ampere

21. The electro magnets are made using the _____ effect of electric current.
Answer:
magnetic

22. Usually the resistance of a conductor _____ with the rise in temperature.
Answer:
increases

23. The SI unit of current is _____.
Answer:
ampere.

24. In Ohm’s law, the _____ and other physical conditions are remaining constant.
Answer:
temperature

25. The temperature remaining constant, the resistance between two opposite forces of a unit cube of a conductor is called its _____.
Answer:
specific resistance.

26. The watt-hour is the practical unit of _____ energy.
Answer:
electrical.

27. Like charges _____ each other.
Answer:
repel

28. SI unit of electric potential is _____.
Answer:
volt.

29. Electric fuse is a _____, device.
Answer:
safety

30. Fleming’s left hand rule is also called _____ rule.
Answer:
motor.

31. An electric generator converts _____ energy into electrical energy.
Answer:
mechanical.

32. The other name of potential difference is _____.
Answer:
voltage

33. The amount of energy given to each coulomb of charge passing through a 12 V battery is _____ J.
Answer:
12

34. The unit of \varepsilon_0 (permitivity in vacuum) is _____.
Answer:
C² N^-1 m^-2

35. Resistivity of silver _____ with increase in temperature.
Answer:
increases

36. An ideal cell should have _____ internal resistance.
Answer:
zero

37. Mica is an _____.
Answer:
insulator

38. _____ filament is used in incandescent bulb.
Answer:
tungsten

39. Tube-lights are _____ power efficient than incandescent bulbs.
Answer:
more

40. CFLs and LED bulbs are _____ efficient than filament-type bulb.
Answer:
more

41. More the number of stars in an electrical appliance, _____ is its efficiency.
Answer:
higher

42. SI unit of magnetic field strength is _____.
Answer:
Tesla

43. The magnetic effect of current was discovered by _____.
Answer:
Oersted

44. The direction of induced current can be predicted by _____ law.
Answer:
Lenz’s

45. Laws of electromagnetic induction was proposed by _____.
Answer:
Faraday

46. In our houses, we have electric supply of frequency _____ Hz.
Answer:
50

47. In an alternator, the stator consists of the _____.
Answer:
armature.

48. The house wiring is done in a ______ system.
Answer:
tree

49. The earth wire should be connected to the _____ of the appliance.
Answer:
body

State whether the following statement is True or False : VSA

1. An ammeter is connected in series in a circuit and a voltmeter is connected in parallel.
Answer:
True

2. Electric current is the flow of charge.
Answer:
True

3. Electric current is vector quantity.
Answer:
False

4. All types of conductors obey ohma’s law
Answer:
False

5. Below 4.2K, mercury behaves as a superconductor.
Answer:
True

6. Resistance of materials in superconducting state is infinity high.
Answer:
False

7. If current flowing through a wire is doubled, the heat produced will also be doubled.
Answer:
False

8. An incandescent bulb is an energy efficient bulb.
Answer:
False

9. Watt is a much smaller unit of electrical power.
Answer:
True

10. We should buy electrical appliance with lower star-rating.
Answer:
False

11. Barlow’s wheel works on alternating current.
Answer:
False

12. At the centre of the circular loop, the magnetic field line is straight.
Answer:
True

13. Lenz’s law is in accordance with the law of conservaion of energy.
Answer:
True

14. A direct current can be stepped up for transmission.
Answer:
False

15. The earth is considered to be at zero potential.
Answer:
True

Well structured WBBSE Class 10 Physical Science MCQ Questions Chapter 7 Atomic Nucleus can serve as a valuable review tool before exams.

Atomic Nucleus Class 10 WBBSE MCQ Questions

Multiple Choice Questions :

Question 1.
Radioactive disintegration differs from a chemical change in being
(A) a nuclear process
(B) an exothermic process
(C) a sponteneous process
(D) a unimolecular first order reaction
Answer:
(A) a nuclear process

Question 2.
The phenomenon of radioactivity was first discoverd by –
(A) Rutherford
(B) Henry Becquerel
(C) Niels Bohr
(D) Madam curie
Answer:
(D) Modam curie.

Question 3.
a-rays consist of a stream of –
(A) H⁺
(B) He²⁺
only electrons
(D) only neutrons
Answer:
(B) He

Question 4.
Which of the following radiations, the one most easily stopped by air is –
(A) X-rays
(B) α-rays
(C) β-rays
(D) γ-rays
Answer:
(A) X-roys

Question 5.
γ-rays –
(A) consist of (+) ve particles
(B) are energy waves
(C) are deflected by an electric field
(D) have mass
Answer:
(B) are energy waves

Question 6.
A device used for the measurement of radioactivity is –
(A) mass spectrometer
(B) cyclotron
(C) nuclear reactor
(D) G-M-counter
Answer:
(D) G-M-counter

Question 7.
If a radioactive element is placed in an evacuated container, its rate of disintegration –
(A) will be increased
(B) will be decreased
(C) will change very slightly
(D) will remain unchanged
Answer:
(D) will remain unchanged

Question 8.
Emission of a β-particle by an atom of an element results in the formation of its
(A) isotope
(B) isomer
(C) isobar
(D) isomorph
Answer:
(C) isobar

Question 9.
Which of the following combinations will give the most stable nuclei?
(A) Odd Z and odd N
(B) Even Z and even N
(C) Odd Z and even N
(D) Even Z and odd N
Answer:
(B) Ever Z and even N

Question 10.
Stable nuclides cannot be obtained for –
(A) Z = 43, N = 35
(B) Z = 61, Z = 89
(C) A > 209
(D) All of these
Answer:
(D) All of thest

Question 11.
Which of the following nuclei are stable?
(A) \({ }_{28}^{60} \mathrm{Ni}\)
(B) \({ }_6^{11} \mathrm{C}\)
(C) \({ }_92²³3} \mathrm{U}\)
(D) \({ }_4^{8} \mathrm{Be}\)
Answer:
(D) \({ }_4^{10} \mathrm{Be}\)

Question 12.
Which of the following nuclel is unstable ?
(A) \({ }_5^{10} \mathrm{C}\)
(B) \({ }_7^{14} \mathrm{N}\)
(C) \({ }_8^{16} \mathrm{O}\)
(D) \({ }_4^{10} \mathrm{Be}\)
Answer:
(D) \({ }_4^{10} \mathrm{Be}\)

Question 13.
One becquerel of radioactivity of equal to –
(A) one disintegation/s
(B) two disintegration/s
(C) 6.023 × 10²³ disintegration/s
(D) three disintegration/s
Answer:
(A) one disintegation/s

Question 14.
The emission of beta-particles is from-
(A) the valence shell of an atom
(B) the inner shell of an atom
(C) the nucleus due to the nuclear conversion proton → neutron + electron
(D) the nucleus due to the nuclear conversion neutron → proton + electron.
Answer:
(D) the nucleus due to the nuclear conversion neutron → proton + electron.

Question 15.
Which of the following processes causes the emission of an x-ray?
(A) Alpha emission
(B) Gamma emissionz`
(C) Positron emission
(D) Electron capture
Answer:
(D) Electron capture

Question 16.
Loss of β-particle is equivalent to –
(A) increase of one proton
(B) decrease of one neutron
(C) combination of both (A) and (B)
(D) None of the above
Answer:
(C) combination of both (A) and (B)

Question 17.
Choose the incorrect one –
(A) 1 curie = 3.7 × 10¹⁰ ds^-1
(B) 1 rutherford = 10⁶ ds^-1
(C) 1 becquerel = 1 ds^-1
(D) 1 fermi = 10³ ds^-1
Answer:
(D) 1 fermi = 10³ ds^-1

Question 18.
Which of the following is the man-made redioactive disintegration series?
(A) Thorium series
(B) Neptunium series
(C) Uranium series
(D) Actinium series
Answer:
(B) Neptunium series

Question 19.
Temperature has no effect on the rate of decay because –
(A) nuclear energies are low
(B) radioactive decay is a statistical process
(C) nuclear energies are very high
(D) radioactive decay follow exponential law
Answer:
(C) nuclear energies are very high

Question 20.
Mark the correct relation-
(A) N₀ = N e ^λt
(B) τ = 1.44 t_0.5
(C) N = N₀ (\(\frac{1}{2}\))ⁿ
(D) t_0.5 = λ ln²
Answer:
(D) t_0.5 = λ ln²

Question 21.
Which one of the following is not a synthetic elements?
(A) U
(B) Cm
(C) Np
(D) PU
Answer:
(A) U

Question 22.
Choose the natural element among the following –
(A) technetium
(B) neptunium
(C) astatine
(D) uranium
Answer:
(D) uranium

Question 23.
Which is not correctly matched here?
(A) Polonium was discovered by Madam curies
(B) Natural radio activity discovered by Henry Becqueral
(C) Maximum penetration power is of α-rays
(D) γ-rays was discovered by willard
Answer:
(C) Maximum penetration power is of α-rays

Question 24.
Positron is the name given to an atom like combination formed between-
(A) a positron and a proton
(B) a positron and a neutron
(C) a positron and α-partical
(D) a positron and an electron
Answer:
(D) a positron and an electron

Question 25.
Which of the following are β – emitters ?
(A) Carbon-14
(B) Cobalt – 60
(C) Tritium – 3
(D) All of these.
Answer:
(D) All of these

Question 26.
Which of the following has highest value for its radioactivity ?
(A) 1 g of Ra
(B) 1 g of Ra so₄
(C) 1 g of Ra Br₂
(D) All of the above have same value
Answer:
(A) 1 g of Ra

Question 27.
Which of the following are α-emitters ?
(A) Helium-5
(B) Tritium
(C) Polonium-212
(D) None of these
Answer:
(C) Polonium-212

Question 28.
In radioactive decay, the emitted electrons come from the-
(A) innermost shell of the atom
(B) outermost shell of the atom
(C) K-shell of an atom
(D) decay neutrons in the nucleus.
Answer:
(D) decay neutrons in the nucleus.

Question 29.
Which emits b-particle?
(A) \({ }_1^3 \mathrm{H}\)
(B) \({ }_6^{14} \mathrm{C}\)
(C) [\({ }_{19}^{40} \mathrm{~K}\)
(D) All of these.
Answer:
(D) All of these.

Question 30.
\({ }_1^3 \mathrm{Al}\) is a stable isotope. It is expected to disintegrate by-
(A) α-emission
(B) β^– -emission
(C) β⁺-emission
(D) proton emission
Answer:
(B) β-emission

Question 31.
Of the following which is not used as a moderator in a nuclear reactor?
(A) Heavy water
(B) Graphite
(C) Beryllium
(D) Sodium
Answer:
(D) Sodium

Question 32.
Control rods used in the nuclear reactor are made of-
(A) nickel
(B) graphite
(C) iron
(D) cadmium
Answer:
(D) cadmium

Question 33.
The moderator used in atomic pile is-
(A) heavy water
(B) uranium
(C) cadmium
(D) iron
Answer:
(A) heavy water

Question 34.
Control rods of nuclear reactor are made up of-
(A) Cd
(B) copper
(C) diamond
(D) graplite
Answer:
(A) Cd

Question 35.
In a nuclear reactor, heavy water is used-
(A) to provide high speed neutrons
(B) to increase the speed of neutrons
(C) to capture neutrons produced by nuclear fission
(D) to transfer the heat from the nuclear reactor
Answer:
(D) to transfer the heat from the nuclear reactor

Question 36.
Near nuclear reactor there is-
(A) large neutron flux
(B) large proton flux
(C) large γ-ray flux
(D) large particles flux
Answer:
(A) large neutron flux

Question 37.
Which of the following isotopes is used in establishing the reaction mechanism of photosynthesis in plants?
(A) \({ }_6^{12} \mathrm{C}\)
(B) \({ }_6^{13} \mathrm{C}\)
(C) \({ }_6^{14} \mathrm{C}\)
(D) \({ }_1^{2} \mathrm{H}\)
Answer:
(C) \({ }_6^{14} \mathrm{C}\)

Question 38.
Which of the following radioactive elements is soluble in water?
(A) Radium
(B) Radon
(C) Technetium
(D) Tritium
Answer:
(B) Radon

Question 39.
Decrease in atomic number is not observed during-
(A) α-emission
(B) β-emission
(C) positron
(D) electron capture
Answer:
(B) β-emission

Question 40.
The relative penetrating power of α, β, γ and neutron (n) follows the order-
(A) α > β > γ > n
(B) n > γ > β > α
(C) β > α > n > γ
(D) None of these
Answer:
(B) n > γ > β > α

Question 41.
Which of the following nuclear reactions will generate an isotope?
(A) Neutron particle emission
(B) Positron emission
(C) α-particle emission
(D) β-particle emission
Answer:
(A) Neutron particle emission

Question 42.
Identify the nuclear reaction that differs from the rest-
(A) positron emission
(B) K-capture
(C) β-decay
(D) γ-decay
Answer:
(D) γ-decay

Question 43.
What is the order of reaction of the decay of ²³5{ _{92 U ?
(A) Zero
(B) first
(C) second
(D) third
Answer:
(B) first

Question 44.
Which of the following has maximum n / P ratio ?
(A) \({ }^{16} \mathrm{Ne}\)
(B) \({ }^{16} \mathrm{O}\)
(C) \({ }^{16} \mathrm{F}\)
(D) \({ }^{16} \mathrm{N}\)
Answer:
(D) \({ }^{16} \mathrm{N}\)

Question 45.
The half life of a radio isotope depends upon-
(A) the amount of isotope
(B) the temperature
(C) the pressure
(D) none of the above
Answer:
(D) none of the above

Question 46.
Which of the following has magic number of protons and neutrons?
(A) \({ }_8^{17} \mathrm{O}\)
(B) \({ }_13^{27} \mathrm{Al}\)
(C) \({ }_9^{17} \mathrm{Al}\)
(D) \({ }_40^{40} \mathrm{Al}\)
Answer:
(D) \({ }_40^{40} \mathrm{Al}\)

Question 47.
India conducted an underground nuclear test at-
(A) Tarapur
(B) Narora
(C) Pokhran
(D) Pushkar
Answer:
(D) Pokhran

Question 48.
Positron has mass equal to –
(A) eletron
(B) α-particle
(C) proton
(D) deutron
Answer:
(A) elecron

Question 49.
\({ }_1^1 \mathrm{H}\) + \({ }_1^3 \mathrm{H}\) (B) \({ }_2^4 \mathrm{He}\) represents –
(A) β-decay
(B) fusion
(C) fission
(D) d-decay
Answer:
(B) fusion

Question 50.
Choose the element which is not radioactive-
(A) Cm
(B) No
(C) Mo
(D) Md
Answer:
(C) Mo

Question 51.
Who discovered radioactivity :
(A) Bacquerel
(B) Madam curie
(c) Peary curie
(D) Ruther ford
Answer:
(A) Bacquerel

Question 52.
Which of the following rays has higher penetrating power ?
(A) sun ray
(B) β-ray
(c) α-ray
(D) γ-ray
Answer:
(D) γ-ray

Question 53.
Which ray is negatively charged ?
(A) α-ray
(B) β-ray
(C) γ-ray
(D) x-ray
Answer:
(B) β-ray

Question 54.
Due to emission of a β-particle the mass of the daughter element :
(A) Increased by one unit
(B) Decreased by one unit
(C) Remains the same
(D) Decreased by two unit
Answer:
(C) Remains the same

Question 55.
Binding energy is :
(A) Bonding between two atoms
(B) Fission of a covalent bond
(C) Binding among the nucleons in nucleus
(D) None of these
Answer:
(C) Binding among the nucleons in nucleus

Question 56.
Nuclear fission is initiated by :
(A) slow neutron
(B) fast neutron
(C) by proton
(D) by α-particle
Answer:
(A) slow neutron

Question 57.
Nuclear energy is :
(A) renewable
(B) not renewable
(C) sometime renewable
(D) it is a matter of debate
Answer:
(B) not renewable

Question 58.
The radioactive isotope used in atom bomb is :
(A) Ra-226
(B) U-238
(C) C-14
(D) U-235
Answer:
(D) U-235

Question 59.
Source of energy of sun is :
(A) Fission reaction
(B) Fusion reaction
(C) Spalation reaction
(D) None of these
Answer:
(B) Fusion reaction

Question 60.
Which nuclear decay emission consists of energy only?
(A) alpha particle
(B) beta particle
(C) gamma radiation
(D) positron emission
Answer:
(C) gamma radiation

Question 61.
Which of the following is the correct order of ionising power for α β, and γ ravs?
(A) α > β > γ
(B) α > γ > β
(C) γ > β > α
(D) β > α > γ
Answer:
(A) α > β > γ

Question 62.
Electromagnetic wave among the radloactive rays is :
(A) α-rays
(B) β-rays
(C) γ-rays
(D) cathode rays
Answer:
(c) γ-rays

Question 63.
Which one among the following nuclet has the lowest n:p ratio?
(A) Hydrogen
(B) Deuterium
(C) Tritium
(D) Helium
Answer:
(A) Hydrogen

Question 64.
Number of neutrons in a α-particle is :
(A) 1
(B) 2
(C) 3
(D) 4
Answer:
(B) 2

Question 65.
Identify the wrong statement :
(A) Radioactivity is a nuclear phenomena
(B) Emission of radioactive rays depends on the number of valence electrons
(C) Radioactivity was first discovered by Becquerel
(D) Three types of radiations are emitted during radiation from a radioactive element.
Answer:
(B) Emission of radioactive rays depends on the number of valence electrons.

Question 66.
Atom bomb was first used in war during
(A) World war II
(B) Gulf war
(C) Cuban war
(D) Indo-Pak war in 1965
Answer:
(A) World war II

Question 67.
Nuclear fission is initiated by :
(A) slow neutron
(B) proton
(C) fast neutron
(D) α particle
Answer:
(A) slow neutron

Question 68.
At around what mass number is the binding energy per nucleon greatest?
(A) 26
(B) 58
(C) 111
(D) 235
Answer:
(B) 58

Question 69.
The nuclear reaction \({ }_1^2 \mathrm{H}\) + \({ }_1^2 \mathrm{H}\) → \({ }_2^4 \mathrm{He}\) is called :
(A) fission reaction
(B) fusion reaction
(C) chain reaction
(D) thermal reaction
Answer:
(B) fusion reaction

Fill in the blanks :

1. Due to the large mass, a-particles possess large ______.
Answer:
Kinetic energy.

2. β-particles are _______ charged.
Answer:
negatively

3. γ-rays are _______.
Answer:
neutral

4. γ-rays have least effect on _______.
Answer:
photographic plates

5. Isotopes of the same element possess same number of _____.
Answer:
protons

6. Accroding to Einstein’s equation, the relationship between mass and energy can be written as ______.
Answer:
E = m c²

7. Atoms of the same element having same atomic number but different atomic masses are called ______.
Answer:
isotopes

8. Atoms of the different elements paossessing same mass number are called _____.
Answer:
Isobars.

9. Isotones are the nuclides having same number of ______.
Answer:
neutrons.

10. Atoms of the same element possessing identical atomic mass but differing in half-life period are called ______.
Answer:
nuclear isomers.

11. The phenomenon of spontaneous emission of invisible radiation is called ______
Answer:
radioactivity

12. β-particles are nothing but ______ moving with high speeds.
Answer:
electrons

13. Electrically neutral electromagnetic waves ejected during radioactive disintegration are called ______.
Answer:
γ-rays.

14. The phenomenon in which a stable nuclide is converted artificially into a radioactive substance is called _____.
Answer:
artificial radioactivity.

15. The speed of γ-rays is ______ speed of light.
Answer:
equal to

16. Atom bomb is based on nuclear _______ reaction.
Answer:
fission

17. Hydrogen bomb is based on nuclear _______ reaction.
Answer:
fusion

18. Source of the energy of the Sun is ______.
Answer:
fusion

19. The time taken for decay of half the initial amount of a radioactive nuclide is called _____.
Answer:
half-life period.

20. The energy required to separate a nucleus into its individual nucleons is known as _______.
Answer:
binding energy

21. The number of neutrons in a radioactive isotope of hydrogen is _____.
Answer:
2

22. The rate of disintegration of active nucleus is known as ______.
Answer:activity

23. \({ }_1^2 \mathrm{H}+{ }_1^3 \mathrm{H} \rightarrow{ }_2^4 \mathrm{He}\) is a _____ reaction.
Answer:
fusion

24. The mass defect in the formation of boron atom \(\frac{1}{5}\) B is 0.0810 amu. The binding energy per nucleon is ______.
Answer:
6.86 MeV

25. \({ }_7^{14} \mathrm{~N}+{ }_0^1 \mathrm{n}\) → ________ + \({ }_7^{14} \mathrm{H}\)
Answer:
{ _6^{-14 C

26. A radioactive nucleus decay emitting one α and two β particles, the daughter nucleus is _______ of the parent.
Answer:
isotope.

27. Particles having energy of several hundred MeV are known as _______.
Answer:
Superfast particles

28. An element \({ }_{\mathbf{Z}}^{\mathbf{A}} \mathbf{M}\) undergoes α-emission followed by two successive β-emissions. The element formed is _______.
Answer:
\(\mathrm{A}_z^{-4} \mathrm{M}\)

29. The end products in the natural disintegration series are stable isotopes of _____.
Answer:
lead

30. One curie of activity is equal to _______ disintegrations per second.
Answer:
3.7 × 10¹⁰

31. The energy equivalent to 1 amu is ______ MeV.
Answer:
931.5

32. The density of the nucleus is of the order of ______ g/cm³.
Answer:
10¹⁴

33. The difference between the total mass of the particles present in the nucleus of a nuclide and its real mass is called ______.
Answer:
mass defect

34. In exoergic reaction, the total mass of the products is _______ than the total mass of the reactants.
Answer:
less.

35. _______ is the inventor of neutron.
Answer:
J. Chadwick.

36. N₂O and CO₂ are the examples of ________.
Answer:
isosters

37. Magic numbers are 2, 8, 20, 50, 82 and ______.
Answer:
126

38. Radioactivity was proposed by ______.
Answer:
Madam curie.

39. Measurement of radioactivity is done by ______.
Answer:
Geiger-Muller counter.

40. The process of transforming one element into other is known as _______.
Answer:
alchemy.

41. Radioactivity was discovered by _______.
Answer:
Becquerel

42. Charge of an α-particle is _______.
Answer:
+2

43. β – particles are emitted from the _______ of the atom.
Answer:
nucleus.

44. \({ }^{60} \mathrm{C}_0\) isotope is used for the treatment of ______.
Answer:
cancer

45. \({ }^{226}{ }_{8 R} R a\) is a _______ element.
Answer:
radioactive

46. Bombardment of one U-235 with one neutron producer ______ neutrons.
Answer:
3

47. chernobyl located in _______.
Answer:
ukraine

48. One gram U-235 generates ________ kW/h electric energy.
Answer:
20,000

49. Fusion reaction occurs at _______ temperature.
Answer:
10⁶ K.

50. The inert gas present in each series is ________.
Answer:
Radon

51. The first radioactive element discovered was __________.
Answer:
uranium

52. In transformation series, radioactivity finally ceases with a a stable __________ isotope as the end product.
Answer:
lead

53. __________ is preceded by a fission reaction.
Answer:
Fusion

54. In a nuclear reactor, the part which consists of the moderator and fuel rods is known as _________.
Answer:
reactor core

55. ‘Atom bomb’ utilizes the ___________ reaction.
Answer:
fission

56. According to theory of relativity, mass can be converted to __________ and vice versa.
Answer:
energy

57. Natural uranium with extra U-235 added into it is called ___________.
Answer:
enriched uranium

58. The name of the aeroplane which dropped atom bomb on Hiroshima is ___________.
Answer:
Enola Gay

Q59. On an average ____________ neutrons are produced per each fission.
Answer:
2.5

State whether the following statement is True or False : VSA

1. Radioactivity depends on the number of electrons in the valence shell.
Answer:
False

2. The instability of nucleus in radioactive atoms is caused by the ratio of neutrons and protons in the nucleus.
Answer:
True

3. Radioactivity is a nuclear phenomena.
Answer:
True

4. Due to emission of a beta particle, mass number of the daughter element is decreased by 1 unit.
Answer:
False

5. When metallic radium is converted to radium chloride, it shows a change in the property of radioactivity.
Answer:
False

6. Radioactive tracer technique is used by researchers and medical practitioners.
Answer:
True

7. Fusion is basically just opposite to fission.
Answer:
True

8. Binding energy owes its origin to mass defect.
Answer:
True

9. Fission reaction releases a large amount of energy.
Answer:
True

10. Inside the thermal reactor, the control rods slow down the neutrons to stimulate further fission.
Answer:
False

11. Nuclear reactor is used to safely convert nuclear energy into electricity.
Answer:
True

12. Atom bomb is based on principles of thermonuclear fusion.
Answer:
False

13. Energy of the stars is attributed to nuclear fission reactions.
Answer:
False

14. The nuclear disaster in Fukushima was initiated after a Tsunami.
Answer:
True

Comprehensive WBBSE Class 10 Physical Science Notes Chapter 4 Thermal Phenomena can help students make connections between concepts.

Thermal Phenomena Class 10 WBBSE Notes

Heat: It is a form of energy which produces sensation of warmth.

Different types of motion:

• Translational motion: Motion along a straight line.
• Vibrational motion: Motion of the molecules about a mean position.
• Rotational motion: Rotation of the molecules about their axes.

Definition of heat with respect to motion: Heat possessed by a body is the total thermal energy of the body and is the sum of kinetic energies of all the individual molecules forming the body due to translational, vibrational and rotational motions of the molecules.

Unit of heat:

• CGS : Calorie
• SI : Joule

One calorie : It is the quantity of heat required to raise the temperature of 1 g water through 1°C

Relation between calorie and Joule : 1 Calorie = 4.18 Joule

Temperature : It is the thermal condition of a body which would determine the direction of flow of heat, when the body is placed in thermal contact with another body.

Measurement of Temperature: Temperatures are measured with a thermometer.

Upper fixed point: It is the temperature of steam from water boiling under a pressure of 76 cm of mercury at sea level and 45° latitude.

Lower fixed point: It is the temperature of melting ice under the same conditions.

Fundamental Internal: The difference between the fixed points of a scale is called fundamental internal.

Different scales of temperature commonly used:

• Celsius scale (by Anders celsius, 1710 , upper fixed point 100°C and Lower fixed point 0°C)
• Fahrenheit scale (by Gabriel Fahrenheit, 1717, upper fixed point = 212° Fand lower fixed point 32°F).
• Absolute or Kelvin scale.

Relation between Celsius and Fahrenheet scale:

\(\frac{C}{5}=\frac{F-32}{9}\)

Relation between Celsius and Kelvin scale :

C = K-273.15

Thermal Expansion : Dimensions of all substances generally increases with increase in temperature. This phenomenon is known as thermal expansion.

Types of expansions in solids:

• Linear expansions
• Superficial expansions
• Volume expansions

Coefficient of linear expansion: The coefficient of linear expansion may be defined as the fractional increase in length of a solid per degree rise in temperature.

[α = \(\frac{l_2-l_2}{l_1\left(t_2-t_1\right)}\)]

[l₁ and l₂ are the lengths of a bar at temperatures t₁ and t₂° respectively, α = coefficient of linear expansion]

Coefficient of Superficial Expansion: The co-efficient of superficial or surface expansion of a solid is defined as the fractional change in surface area of the solid per degree rise in temperature.

[β = \(\frac{s_2-s_1}{s_1\left(t_2-t_1\right)}\)]

[s₁. and s₂ are the surface areas of a solid at t₁° and t₂° respectively, β = coefficient of superficial expansion]

Coefficient of cubical expansion: The coefficient of cubical or volume expansion of a solid is defined as the fractional increase in volume of the solid per degree rise in temperature.

[γ = \(\frac{v_2-v_1}{v_1\left(t_2-t_1\right)}\)]

[v₁. and v₂ are the volumes of a solid t₁° and t₂° respectively, γ = coefficient of superficial expansion]

Coefficient	Unit	Dimension
α	K-1 or °C-1 or °F-1	l-1
β	K-1 or °C-1 or °F-1	l-1
γ	K-1 or °C-1 or °F-1	l-1

Relation among α, β and γ : \(\left[\alpha=\frac{\beta}{2}=\frac{\gamma}{3}\right]\)

Various applications of solids in our daily life:

• Thermostat Fire Alarm
• Bimetallic Thermometer
• Compensating Rod Type Pendulum
• Harrison’s Grid-iron Pendulum

Apparent expansion of the liquid: If the expansion of the liquid is measured ignoring the expansion of the containing vessel, the expansion is called the apparent expansion of the liquid.

Real expansion of the liquid: When the actual expansion of the liquid is measured by considering the expansion of the containing vessel, it is called real expansion of the liquid.

Real expansion of the liquid = expansion of the vessel + apparent expansion of the liquid

Co-efficient of real expansion of liquids: The coefficient of real or absolute expansion of a liquid is the fraction of its volume

γ_r = \(\frac{v_2-v_1}{v_1\left(t_2-t_1\right)}\)

(v₁ is the initial volume of a given mass of a liquid at t₁° and v₂ is the real volume of the same mass of the liquid at t₂°, γ_r is the coefficient of real expansion of the liquid).

Co-efficient of apparent expansion of liquids: The coefficient of apparent expansion of the liquid is the traction of its volume by which the liquid appears to expand per degree rise in temperature.

[γ_r = \(\frac{v_2-v_1}{v_1\left(t_2-t_1\right)}\)]

(v₂ is the apparent volume of the liquid at t₂°, γ_a is the coefficient of apparent expansion of the liquid).

Relation between expansion coefficients of a liquid:

(γ_r. is the coefficient of real expansion of the liquid, γ_a is the coefficient of apparent expansion of the liquid). γ_s is the coefficient of cubic expansion of the material of the vessel)

γ_r = \(\frac{v_2^{\prime}-v_1}{v_1\left(t_2-t_1\right)}\)

Variation of density of a liquid with temperature: Let m mass of a liquid has volumes v₁ and v₂ at temperatures t₁° and t₂° respectively. If ρ₁ and ρ₂ be the densities of the liquid at t₁° and t₂° respectively and if γ_r, be the coefficient of real expansion of the liquid then,

When a liquid is more expansible than the material of the vessel, there will be, on the whole, an apparent expansion of the liquid. In the reverse case, the liquid will apparently cantact. If two expand equally, the volume of the liquid will appears to remain constant.

A hollow vessel expands as if it were solid having the same volumes, because if the hollow of the vessel were also solid, after expansion it would fit in with outer vessel.

Anomalouis expansion of water: Usually liquids expand on heating. But in the case of water we find deviation from this general behaviour of the liquids within a certain range of temperature. The volume of water is minimum at 4°C and hence its density is maximum at 4°C. This phenomenon is called the anomalous expansion of water.

Conclusion of Hope’s experiment: From Hope’s experiment it is proved that water at bottom which is denset is at 4°C. After sufficiently long time the temperature of the lower thermometer falls slightly due to loss of heat by conduction to the upper regions.

Effect on Marine life: Anomalous expansion of water has great practical importance on the marine life in the cold countries. The temperature of the deeper layers of the water in the pond remains nearly at 4°C and falls gradually at 0°C upwards till the layer of ice is reached. The marine life in the water is thus saved. For the same reason temperature of the bottom of a deep sea remains constant (i.e. 4°C ) throughout the year.

Expansion of a gas at constant Temperature:

Boyle’s Law: The volume of a fixed mass of a gas of constant temperature is inversely proportional to its pressure.

V ∝ \(\frac{1}{P}\) (At constant temperature P is the pressure and V is the volume of a fixed mass of gas)
or V ∝ \(\frac{K}{P}\) (K is the proportionality constant. It depends
or, PV = K = constant

• the mass of the gas
• nature of the gas
• temperature of the gas)

Expansion of a Gas at constant Pressure :

Charles’ Law: The pressure remaining constant, the volume of a given mass of any gas increases (or decreases) by the constant fraction \(\frac{1}{273}\)of its volume of 0°C, for every degree celsius increase (or decrease) of temperature.

V_t = V₀(1 ± \(\frac{t}{273}\))
v₀ and v_t are the volumes of a given mass of gas at 0°C and t°C respectively, the pressure of the gas remaining constant all through)

Expansion of gas at constant volume:

Pressure Law: Volume remaining constant, the pressure of a given mass of a gas increases (or decreases) by a constant fraction \(\frac{1}{273}\)of its pressure at 0°C for each degree celsius increase (or decrease) of temperature.

P_t = P₀(1 ± \(\frac{t}{273}\))

(P₀ and P_t are the pressures of a given mass of gas at 0°C and t°C respectively, the volume of the gas remaining constant all through)

Volume Coefficient (γ_p) : The volume coefficient of a gas is the fractional increase in the volume of the gas at 0°C for each degree celsius rise in temperature, the pressure remaining constant.

V_t = V₀(1 + γ_p t)

From Charles’ Law, we find γ_p = \(\frac{1}{273}\)°C^-1 = 36.6 × 10_-4 °C^-1

Pressure Coefficient (γ_ν): The pressure coefficient of a gas is the fractional increase in pressure of the gas at 0°C for each degree celsius rise in temperature, the volume remaining constant

P₁ = P₀(1 + γ_v t)

From Pressure law, we find that γ_v = \(\frac{1}{273}\)°C^-1 = 36.6 × 10_-4 °C^-1

Equality of volume and pressure coefficients : Consider a given mass of a gas at °C having pressure and volume P₀ and V₀ respectively. It is heated to a temperature t°C in two alternative ways viz (I) at constant volume, when pressure changes to a P_t or (II) at constant pressure, when the volume changes to V_t.

In the case I, Pressure Law’s is applicable,

so P_t = P₀(1 + γ_v t)

In case II, Charle’s law is applicable, so V_t = V₀(1 + γ_v t)

In both the cases final temperature is t°C and so according to Boyle’s Law

P_t V₀ = P₀ V_t
or, P₀ V₀(1 + γ_v t) = P₀ V₀(1 + γ_{p</sub t)
∴ γv = γr}

Ideal gas and Ideal gas equation: A gas which obeys gas laws is called. A gas which obeys gas laws is called an ideal gas. An ideal gas equation is PV = nRT (R = universal gas constant)

Speciefic heat capacity: Specific heat capacity of a substance is the amount of heat required to rise the temperature of unit mass of the substance through one degree.

Specific heat of water:

• 1 cal g^-1 °C^-1 : CGS system
• 4200 Jkg^-1 K^-1 : SI system.

Molar specific heat capacity: Molar specific heat capacity of a substance is the amount of heat required to raise the temperature of one gram mole of the substance through a unit degree.

Molar specific heat at constant volume (C_v) : The molar specific heat of a gas at constant volume (C_v) is the amount of heat required to raise the temperature of one mole of the gas through one degree keeping the volume constant throughout.

Molar specific heat at constant pressue (C_p) : The molar specific heat of a gas at constant pressure (Cp) is the amount of heat required to raise the temperature of one mole of the gas through one degree keeping the pressure constant throughout.

C_p is greater than C_v

Thermal capacity: Thermal capacity of a substance is the quantity of heat required to raise the temperature of it by 1°.

Water equivalent: Water equivalent of a body is the mass of water which will be heated through 1° by the amount of heat that raises the temperature of the body through 1°.

Fundamental principle of calorimetry
Heat lost by hot body = Heat gained by cold body.

Conditions :

during the process of heat thransfer, there is no heat exchange with the surrounding.
No chemical reaction takes place between the bodies. This is known as fundamental principle of calorimetry.

Latent heat of substance: The amount of heat to be supplied or extracted for changing completely the stake of unit mass of a substance without change of temperature is called the latent heat of the substance for the corresponding change of state.

Melting point and effect of pressure on it :

Melting point: The normal melting point of a solid is the definite temperature at which it melts on heating under normal atmospheric pressure and the temperature remains constant until the melting is complete.

Regelation: The phenomenon of melting of ice under pressure and freezing again on releasing the pressure is called regelation.

Bioling point and e effect of pressure on it:

Bolling point: The normal boiling point of a liquid in the temperature at which a liquid boils under normal atmospheric pressure.

The boiling point of a liquid depends uy on:

• the nature of the liquid
• presence of dissolved substance
• the superincumbent pressure.

Vapour pressure: Whenever a liquid evaporates at any temperature, the vapour exerts a definite pressure on everything in contact. This pressure is called vapour pressure of the liquid at that temperature.

Saturated vapour: If the liquid be allowed to evaporate in a closed space, it is found that after a small time evaporation stops, i.e., t a given temperature, there is a maximum limit to the amount of vapour the space can hold. The space is said to be then saturated with vapour and the vapour is then called saturated vapour.

Difference between Gas and Vapour-Critical Temperature: For every substance in gaseous state there is a certain temperature such that if the substance be below this temperature, it can be liquefied by the application of suitable pressure, and if above this temperature, it cannot be liquified, however large the pressure may be, then the temperature is called the critical temperature for that substance.

Thus a gaseous substance at a temperature above critical temperature is called gas and when it is at a temperature below its critical temperature it is called vapour.

Thermal conduction

Conduction: Conduction is the process of transfer of heat through a substance without any detectable motion of the particles of the substance.

Good conductors: The substances through which heat is conducted easily from one region to the other are called good conductors.

Bad conductors or Insulators: The substances through which heat is not conducted easily from one region to the other are called bad conductors or insulators.

Coefficient of thermal conductivity: The coefficient of thermai conductivity at the material of a substance is numerically equal to the quantity of heat that conducts in one second normally through a slab of unit length and unit area, the difference of temperature between its end faces being one degree.

Unit of thermal conductivity

CGS: Cal cm^-1 S^-10 C^-1
SI: Jm^-1 S^-1 K^-1 or Wm^-1 k^-1
Dimension: [MLT^-3 θ^-1]

Thermometric conductivity: The rate of rise of temperature during the variable state is proportional to K / P₃ (where K = thermal conductivity of the material, P_s = specific heat). This ratio is known as thermometric conductivity or the thermal conductivity per thermal capacity per unit volume.

Unit of thermometric conductivity:

CGS: cm² s^-1 ; SI: m² s^-1

Dimension of thermometric conductivity: [M⁰ L² T^-1]

Although thermal conductivity of iron is more than that of lead, diffusivity of lead is more and they under similar conditions of heat flow, the temperature of different sections of the lead bar would rise more rapidly than iron bar.

Applications of conductivity:

ICE is packed in saw dust, because air which is bad conductors of heat being trapped in the saw dust prevents transfer of heat from the surrounding to the ice. So ice does not melt.

Cooking utensils are provided with wooden or plastic handles, as wood or plastic are bad conductors of heat, so we can hold the hot utensils with the help of these handles.

Wearing two cotton shirts of half the thickness each is better than a single shirt of double the thickness in winter. There is a layer of bad conductor air entrapped between the two shirts providing additional protection from heat conduction from the body.

In winter, birds often swell their feathers, thereby enclosing air between their bodies and feathers and thus does not allow flow of heat from the bodies of the birds and keeps them warm.

Convection of Heat: Convection is the process by which heat is transmitted through a liquid or gas from a hotter point to a colder point due to the bodily motion of the heated particles of the substances.

It may be noted that although mercury is a liquid, it is heated by conduction and not by canvection.

Radiation: Radiation is the transmission of heat from a hot body to a cold body without the help of any medium and without appreciable heating of the intervening medium if any.

Some basic characteristics of thermal radiations are:

• (i) They travel along straight line with velocity of light.
• They require no medium for their propagation and even if there be intervening medium, the medium is not affected.
• They obey inverse square law i.e. their intensity varies inversely as the square of the distance from the source.
• They can be reflected and refracted like light.
• They also exhibit the phenomena of interference, diffraction and polarisation.

The reflecting power of a body (Reflectance) : It is the ratio of the amount of thermal radiations reflected by the body in a given time to the total amount of thermal radiation incident on the body in the same time.

The absorbing power of a body (absorbtance): It is the ratio of the amount of thermal radiations absorbed by the body in a given time to the total amount of thermal radiations incident on the body in the same time.

The transmitting power of a body (transmittance): It is the ratio of the amount of thermal radiations transmitted through the body in a given time to the total amount of thermal radiations incident on the body in the same time.

Perfectly Black body; A perfectly black body is that which absorbs completely the radiations of all the wavelengths on it.

Kirchoff’s Law : It states that the ratio of emissive power to absortive power corresponding to a particular wavelength and at any given temperature is always a constant for all bodies, the constant being equal to the emissive power of a perfectly black body at the same temperature and corresponding to the same wavelength.

Stefan’s Law: It state that the amount of heat energy emitted per second by unit area of a perfectly black body is directly proportional to the fourth power of absolute temperature of the body.

Wen’s displacement Law: It states that the wavelength of maximum intensity of emission of black body radiation is inversely proportional to the absolute temperature of the body.

Newton’s Law of cooling: It states that the rate of loss of heat of a liquid is directly proportional to the difference in temperatures at the liquid and the surroundings, provided the difference in temperature is small.

Green house effect: Green house effect is an example of selective absorption of heat by glass. The amount of heat transmitted through a substance depends on temperature of the source of heat.

Global warming: CO₂, water vapour, methane, nitrous oxide, tropospheric ozone, chlorofluoro carbon compounds, halogen compounds etc. on increasing the amount of green house gases in the atmosphere, the temperature of earth.

Effect of global warming:

• Possibility of increasing the sea level
• Effect on atmosphere
• Effect on forest and agriculture