CBSE Class 12 Chemistry –Chapter 3 Electrochemistry- Study Materials

Electrochemistry Class 12 Chemistry MCQs

1. A new galvanic cell of E_ext more than E^o (1.1 v)of Daniel cell is connected to Daniel cell in a manner that new cell gives electrons to Zn, what will happen
(a) E_cell will increase
(b) E_cell will decrease
(c) No change will take place
(d) Daniel cell will work as electrolytic cell where Zn will be deposite on zinc rod and copper will dissolve from copper rod.

2. Ag⁺(aq) + e^– → Ag(s) E° = + 0.80 V
Fe²⁺(aq)+ + 2e^– → Fe(s) E° = – 0.44 V
What is emf of
Fe(s) + 2Ag⁺(aq) → Fe²⁺(aq) + 2Ag(s)
(a) 1.16 V
(b) 1.24 V
(c) 2.04 V
(d) -1.16 V

3. A conductivity cell containing electrodes made up of
(a) Gold
(b) Silver
(c) Platinised platinum
(d) Copper

4. Which of the following expression is correct for ‘K_a’ in terms of Λ° and Λ, where ‘C’ is molarity.

5. What is pH of the half cell Pt|H2fe)|H⁺ if \(\mathrm{E}_{\mathrm{H}^{+} \mathrm{H}_{2}}^{\circ}\) =-0.0295 V
(a) 1
(b)2
(c) 0.5
(d) 3

6.

What is the value of ‘K’ for above reaction?
(a) 1 × 10⁸
(b) 1 × 10²
(c) 4 × 10³
(d) 3 × 10⁴

7. Which of the following statement is correct?
(a) E_Cell and ∆_rG of cell reaction both are extensive properties.
(b) E_Cell and ∆_rG of cell reaction both are . intensive properties.
(c) E_Cell is an intensive property while ∆_rG of cell reaction is an extensive property.
(d) E_Cell is an extensive property while ∆_rG of cell reaction is an intensive property.

8. While charging the lead storage battery _________ . [NCERT Exemplar]
(a) PbSO₄ anode is reduced to Pb.
(b) PbSO₄ cathode is reduced to Pb.
(c) PbSO₄ cathode is oxidised to Pb.
(d) PbSO₄ anode is oxidised to PbO₂.

9. On the basis of following E°values, the strongest oxidising agent is

10. Λ of M/32 solution of weak acid is 8 S cm2 mol^-1 and limiting molar conductivity is 400 S cm2 mol1. Ka for acid is
(a) 1.25 × 10^-6
(b) 6.25× 10^-4
(c) 1.25 × 10^-4
(d) 1.25 × 10^-5

Note: In the following questions two or more options may be correct. (Q.11 to Q.14)
11. The positive value of the standard electrode potential of Cu²⁺/Cu indicates that _________ [NCERT Exemplar]
(a) this redox couple is a stronger reducing agent than the H⁺/H₂ couple.
(b) this redox couple is a stronger oxidising agent than H⁺/H₂.
(c) Cu can displace H₂ from acid.
(id) Cu cannot displace H₂ from acid.

12. \(\mathrm{E}_{\text {cell }}^{\circ}\) for some half cell reactions are given below. On the basis of these mark the correct answer. [NCERT Exemplar]

(a) In dilute sulphuric acid solution hydrogen ion will be reduced at cathode.
(b) In concentrated sulphuric acid solution, water will be oxidised at anode.
(c) In dilute sulphuric acid solution, water will be oxidised at anode.
(d) In dilute sulphuric acid solution, \(\mathrm{SO}_{4}^{2-}\) ion will be oxidised to tetrathionate ion at anode.

13. \(\mathrm{E}_{\mathrm{Cell}}^{\ominus}\) = 1.1V for Daniel cell. Which of the following expressions are correct description of state of equilibrium in this cell? [NCERT Exemplar]

14.

15. The charge required for the reduction of 1 mol of MnO₂^– to MnO₂ is
(a) 1 F
(b) 3 F
(c) 5 F
(d) 6 F

16. The cell reaction of the galvanic cell.

17. Which of the following reaction is used to make fuel cell?

18. If limiting molar conductivity of Ca²⁺ and Cl^– are 119.0 and 76.3 S cm² mol^-1, then the value of limiting molar conductivity of CaCl2 will be
(a) 195.3 S cm² mol^-1
(b) 271.6 S cm² mol^-1
(c) 43.3 S cm² mol^-1
(d) 314.3 S cm² mol^-1.

19. NH4NC>3 is used in salt bridge because
(a) it forms a jelly like material with agar-agar.
(b) it is a weak electrolyte.
(c) it is a good conductor of electricity.
(d) the transport number of NH₄⁺ and NO₃^– ions are almost equal.

20.

21. The reaction, 3ClO^– (aq) → ClO₃ (aq) + 2Cl^– (aq) is an example of
(a) Oxidation reaction
(b) Reduction reaction
(c) Disproportionation reaction
(d) Decomposition reaction

22. The emf of the cell:
Ni / Ni²⁺ (1.0 M) // Au³⁺ (1.0 M) / Au (E° = -0.25 V for Ni²⁺/Ni; E° = 1.5 V for Au³⁺/Au) is
(a) 1.25 V
(b) -1.25 V
(c) 1.75 V
(d) 2.0 V

23. The standard emf of a galvanic cell involving cell reaction with n = 2 is formed to be 0.295 V at 25° C. The equilibrium constant of the reaction would be
(a) 1.0 × 10¹⁰
(b) 2.0 × 10¹¹
(c) 4.0 × 10¹²
(d) 1.0 × 10²
[Given F = 96500 (mol^-1); R = 8.314 JK^-1 mol^-1]

24. If E°_Fe²⁺/Fe = -0.441 V and E°_{Fe²⁺/Fe²⁺} = 0.771 V, the standard EMF of the reaction,
Fe + 2Fe³⁺ → 3Fe²⁺ will be
(a) 1.212 V
(b) 0.111 V
(C) 0.330 V
(d) 1.653 V

25. Match the terms given in Column I with the units given in Column II. [NCERT Exemplar]

26. Match the terms given in Column I with the items given in Column II.

27. Match the items of Column I and Column II. [NCERT Exemplar]

Note: In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices. (Q.18 to Q.20)
(а) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
28. Assertion: ECe|, should have a positive value for the cell to function.
Reason: E_cathode, < E_anode . [NCERT Exemplar]

29. Assertion: Am for weak electrolytes shows a sharp increase when the electrolytic solution is diluted.
Reason: For weak electrolytes degree of dissociation increases with dilution of solution. [NCERT Exemplar]

30. Assertion: For measuring resistance of an ionic solution an AC source is used.
Reason: Concentration of ionic solution will change if DC source is used. [NCERT Exemplar]

31. A° for weak electrolyte is determined by _________ .

32. The quantity of change required to obtain 1 mole of Al from Al₂O₃ is _________ .

33. \(\frac{2}{3}\)Al₂O₃ → \(\frac{4}{3}\)Al + 2O₂, number of moles of electrons gained or lost = _________ .

34. If \(\mathrm{E}_{\text {cell }}^{\circ}\) is -ve, cell will not work. [True/False]

35. If external emf opposing Daniel cell is less than 1.10 V, cell will keep in working. [True/False]

36. Salt bridge completes internal circuit and prevents accumulation of charges. [True/False]

37. Inert electrolyte in salt bridge reacts with solution of half cells. [True/False]

38. Represent the galvanic cell in which the reactions is
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s) [Delhi 2013(C)]

39. Consider the following diagram in which an electrochemical cell is coupled to an eletrolytic cell. What will be the polarity of electrodes ‘A’ and ‘B’ in the electrolytic cell?

40. Can absolute electrode potential of an electrode be measured?

41. The standard reduction potential for Zn²⁺(aq)/Zn(s) is – 0.76 V. Write the reactions occurring at the electrodes when coupled with NHE or SHE (standard hydrogen electrode).

42. E° (reduction potential) of Cu and Zn are + 0.34 V and – 0.76 V respectively. Which of them is stronger reducing agent?

43. Predict whether F2 and Na will react with one another. Give reason.

44. Write the correct representation of cell:
2Cr(s) + 3Cd²⁺(aq) → 2Cr³⁺(aq) + 3Cd(s)

45. Fe³⁺(aq) + e^– → Fe³⁺(aq), E° = +0.77 V
Cl₂(g) + 2e^– → 2Cl^–(aq), E° = +1.36 V
Write the reaction which could be feasible using above half cells.

46. If E° for the reaction Fe³⁺(aq) + e^– → Fe²⁺(aq) is + 0.77 V, what will be E° value for the reaction 2Fe³⁺(aq) + 2e^– → 2Fe²⁺(aq)?

47. Write Nemst equation for the following chemical reaction:
2Cr + 3Fe²⁺ → 2Cr³⁺ + 3Fe

48. Can \(\mathrm{E}_{\text {cell }}^{\circ}\) or ∆_rG° for a cell reaction ever be equal to zero?

49. Define specific conductivity (specific conductance).

50. What is meant by cell constant? What is its use?

51. What do you mean by limiting molar conductivity?

52. Complete: Λ° Na₂SO₄ =

53. HCl does not give acidic solution in benzene. Why?

54. How much charge in Faraday is required for the reduction of 1 mol of Ag⁺ to Ag? [AI 2015 Guwahati]

55. How much charge is required for the reduction of 1 mole of Zn²⁺ to Zn? [AI 2015 Patna]

56. How much charge in Faraday is required for reduction of 1 mole of Al³⁺ to AI? [AI 2015 Chennai & Trivandrum; DoE]

57. How many Faradays of charge are required to convert:
1 mole of MnO₄^–“ to Mn²⁺ ion,

58. What mass of zinc (II) ion will be reduced by 1 mole of electrons?

59. How many Faradays are required to liberate 2 moles of hydrogen gas in electrolysis of acidified water?

60. What are the factors which depend on the products of electrolysis?

61. What is primary cell? Give an example.

62. What are secondary cells? [AI 2014]

63. Which electrolyte is used in fuel cell?

64. Why does alkaline medium inhibit rusting of iron?

65. What is the value of potential of SHE?