NCERT BOOK CLASS 12TH CHEMISTRY MCQ
Chapter 2 : Electrochemistry
Important MCQs with Answers
1. How does energy conversion occur in an electrochemical cell?
a) Chemical energy → Electrical energy
b) Electrical energy → Chemical energy
c) Thermal energy → Electrical energy
d) Light energy → Chemical energy
Answer: a) Chemical energy → Electrical energy
2. What happens at the anode in a galvanic cell?
a) Reduction
b) Oxidation
c) Discharge
d) Neutralization
Answer: b) Oxidation
3. Which of the following is not an example of an electrolyte?
a) NaCl
b) H₂SO₄
c) CH₃COOH
d) C₆H₁₂O₆
Answer: d) C₆H₁₂O₆ (Glucose is a non-electrolyte)
4. According to Faraday’s first law of electrolysis, the amount of substance liberated during electrolysis depends on:
a) Time
b) Current
c) Both (a) and (b)
d) Temperature
Answer: c) Both (a) and (b)
5. What is the potential of a Standard Hydrogen Electrode (SHE)?
a) 0.00 V
b) 1.00 V
c) 2.00 V
d) -1.00 V
Answer: a) 0.00 V
6. What is the Nernst equation used for?
a) Calculating cell potential
b) Calculating pH
c) Calculating heat change
d) Calculating pressure
Answer: a) Calculating cell potential
7. Which metal is at the top of the electrochemical series?
a) Gold
b) Lithium
c) Platinum
d) Silver
Answer: b) Lithium
8. The conductivity of an electrolyte solution depends on:
a) Temperature
b) Concentration
c) Both (a) and (b)
d) Pressure
Answer: c) Both (a) and (b)
9. What is the unit of cell constant?
a) ohm⁻¹ cm⁻¹
b) cm⁻¹
c) ohm cm
d) S cm² mol⁻¹
Answer: b) cm⁻¹
10. The unit of specific conductance is:
a) ohm⁻¹ cm⁻¹
b) ohm cm
c) S cm² mol⁻¹
d) cm⁻¹
Answer: a) ohm⁻¹ cm⁻¹
11. The unit of molar conductivity is:
a) ohm⁻¹ cm² mol⁻¹
b) ohm cm
c) S cm⁻¹
d) cm⁻¹
Answer: a) ohm⁻¹ cm² mol⁻¹
12. What is the function of a salt bridge in an electrochemical cell?
a) Maintaining current flow
b) Facilitating ion transfer
c) Maintaining electrical neutrality
d) All of the above
Answer: d) All of the above
13. Which of the following is a primary cell?
a) Lead storage battery
b) Nickel-Cadmium cell
c) Dry cell
d) Lithium-ion cell
Answer: c) Dry cell
14. What is the electrolyte in a lead storage battery?
a) NaOH
b) H₂SO₄
c) HCl
d) KOH
Answer: b) H₂SO₄
15. The value of Faraday’s constant is:
a) 96500 C mol⁻¹
b) 6.022 × 10²³ C mol⁻¹
c) 8.314 J K⁻¹ mol⁻¹
d) 1.602 × 10⁻¹⁹ C
Answer: a) 96500 C mol⁻¹
16. What occurs at the cathode in an electrochemical cell?
a) Oxidation
b) Reduction
c) Discharge
d) Neutralization
Answer: b) Reduction
17. Which of the following is a secondary cell?
a) Dry cell
b) Lead storage battery
c) Mercury cell
d) Zinc-carbon cell
Answer: b) Lead storage battery
18. What happens at the cathode during electrolysis?
a) Reduction of cations
b) Oxidation of anions
c) Decomposition of electrolyte
d) Formation of gas
Answer: a) Reduction of cations
19. How is the EMF (Electromotive Force) of a cell calculated?
a) E°cell = E°cathode – E°anode
b) E°cell = E°anode – E°cathode
c) E°cell = E°cathode + E°anode
d) E°cell = E°anode × E°cathode
Answer: a) E°cell = E°cathode – E°anode
20. Which of the following metals reacts with water to release hydrogen gas?
a) Copper
b) Silver
c) Sodium
d) Gold
Answer: c) Sodium
21. How does current flow in an electrochemical cell?
a) Electrons
b) Ions
c) Both (a) and (b)
d) Protons
Answer: c) Both (a) and (b)
22. Which of the following statements is correct?
a) In a galvanic cell, chemical energy is converted into electrical energy
b) In an electrolytic cell, electrical energy is converted into chemical energy
c) Both (a) and (b) are correct
d) None are correct
Answer: c) Both (a) and (b) are correct
23. Metals lower in the electrochemical series:
a) Are more reactive
b) Are less reactive
c) Do not react with water
d) Do not release hydrogen from acids
Answer: b) Are less reactive
24. Where does oxidation occur in an electrochemical cell?
a) Cathode
b) Anode
c) Salt bridge
d) Electrolyte
Answer: b) Anode
25. Which of the following pairs is correct?
a) Zn²⁺/Zn – E° = -0.76 V
b) Cu²⁺/Cu – E° = -0.34 V
c) Ag⁺/Ag – E° = -0.80 V
d) Fe²⁺/Fe – E° = +0.44 V
Answer: a) Zn²⁺/Zn – E° = -0.76 V
26. The unit of equivalent conductivity of an electrolyte solution is:
a) ohm⁻¹ cm² equiv⁻¹
b) ohm cm
c) S cm⁻¹
d) cm⁻¹
Answer: a) ohm⁻¹ cm² equiv⁻¹
27. In an electrochemical cell, which electrode is the positive electrode?
a) Anode
b) Cathode
c) Salt bridge
d) Electrolyte
Answer: b) Cathode
28. Which of the following is a strong electrolyte?
a) CH₃COOH
b) NH₄OH
c) NaCl
d) H₂CO₃
Answer: c) NaCl
29. The Nernst equation for calculating the EMF (Electromotive Force) of a cell is:
a) Ecell = E°cell – (RT/nF) ln Q
b) Ecell = E°cell + (RT/nF) ln Q
c) Ecell = E°cell × (RT/nF) ln Q
d) Ecell = E°cell / (RT/nF) ln Q
Answer: a) Ecell = E°cell – (RT/nF) ln Q
30. What happens at the anode during electrolysis?
a) Reduction of cations
b) Oxidation of anions
c) Decomposition of electrolyte
d) Formation of gas
Answer: b) Oxidation of anions
31. Which of the following metals does not react with water?
a) Sodium
b) Potassium
c) Iron
d) Gold
Answer: d) Gold
32. In an electrochemical cell, which electrode is the negative electrode?
a) Anode
b) Cathode
c) Salt bridge
d) Electrolyte
Answer: a) Anode
33. Which of the following is a weak electrolyte?
a) HCl
b) NaOH
c) CH₃COOH
d) KNO₃
Answer: c) CH₃COOH
34. Which metal is at the bottom of the electrochemical series?
a) Lithium
b) Sodium
c) Gold
d) Aluminum
Answer: c) Gold
35. How can the conductivity of an electrolyte solution be increased?
a) Increasing temperature
b) Increasing concentration
c) Both (a) and (b)
d) Increasing pressure
Answer: c) Both (a) and (b)
36. In an electrochemical cell, in which direction do electrons flow?
a) Anode to cathode
b) Cathode to anode
c) Salt bridge to anode
d) Electrolyte to cathode
Answer: a) Anode to cathode
37. Which of the following statements is correct?
a) The conductivity of an electrolyte solution increases with temperature
b) The conductivity of an electrolyte solution decreases with temperature
c) Temperature has no effect on conductivity
d) Conductivity always remains constant
Answer: a) The conductivity of an electrolyte solution increases with temperature
38. What type of ions are reduced at the cathode during electrolysis?
a) Cations
b) Anions
c) Neutral molecules
d) None
Answer: a) Cations
39. Which of the following metals releases hydrogen gas when reacting with acid?
a) Copper
b) Silver
c) Zinc
d) Gold
Answer: c) Zinc
40. What is a salt bridge in an electrochemical cell made of?
a) Inert metal
b) Inert gas
c) Inert salt
d) Acid
Answer: c) Inert salt
41. The molar conductivity of an electrolyte solution depends on:
a) Concentration
b) Temperature
c) Pressure
d) Volume
Answer: a) Concentration
42. In an electrochemical cell, how do ions flow?
a) Through the salt bridge
b) Through the external circuit
c) Through the electrodes
d) Through the electrolyte
Answer: d) Through the electrolyte
43. Which of the following is not an electrolyte?
a) NaCl
b) HCl
c) C₂H₅OH
d) H₂SO₄
Answer: c) C₂H₅OH (Ethanol)
44. What type of ions are oxidized at the anode during electrolysis?
a) Cations
b) Anions
c) Neutral molecules
d) None
Answer: b) Anions
45. Which of the following metals does not release hydrogen gas when reacting with water?
a) Sodium
b) Potassium
c) Calcium
d) Copper
Answer: d) Copper
46. In an electrochemical cell, how do electrons flow?
a) Through the salt bridge
b) Through the external circuit
c) Through the electrolyte
d) Through the electrodes
Answer: b) Through the external circuit
47. Which of the following is a strong electrolyte?
a) CH₃COOH
b) NH₄OH
c) NaOH
d) H₂CO₃
Answer: c) NaOH
48. The equivalent conductivity of an electrolyte solution depends on:
a) Concentration
b) Temperature
c) Pressure
d) Volume
Answer: a) Concentration
49. Which of the following pairs is correct?
a) Cu²⁺/Cu – E° = +0.34 V
b) Zn²⁺/Zn – E° = +0.76 V
c) Ag⁺/Ag – E° = -0.80 V
d) Fe²⁺/Fe – E° = -0.44 V
Answer: a) Cu²⁺/Cu – E° = +0.34 V
50. What is the combined process of oxidation and reduction in an electrochemical cell called?
a) Electrolysis
b) Redox reaction
c) Neutralization
d) Combination reaction
Answer: b) Redox reaction
51. The specific conductance of 0.1 M KCl solution is 1.29 S m⁻¹ at 298 K. What will be its molar conductivity?
a) 129 S cm² mol⁻¹
b) 12.9 S cm² mol⁻¹
c) 0.129 S cm² mol⁻¹
d) 1.29 S cm² mol⁻¹
Answer: b) 12.9 S cm² mol⁻¹
Explanation:
Λₘ = (κ × 1000)/M = (1.29 S m⁻¹ × 1000)/0.1 mol m⁻³ = 12900 S cm² mol⁻¹ × 10⁻⁴ = 12.9 S cm² mol⁻¹
52. The standard cell potential of a cell is 1.1 V. If n=2, what will be the standard Gibbs energy change (ΔG°) for the cell reaction? (F = 96500 C mol⁻¹)
a) -212.3 kJ mol⁻¹
b) -110.5 kJ mol⁻¹
c) -55.25 kJ mol⁻¹
d) -424.6 kJ mol⁻¹
Answer: a) -212.3 kJ mol⁻¹
Explanation:
ΔG° = -nFE° = -2 × 96500 × 1.1 = -212300 J mol⁻¹ = -212.3 kJ mol⁻¹
53. The resistance of 0.01 M NaCl solution was measured as 210 Ω. If the cell constant is 0.88 cm⁻¹, what will be the specific conductance (κ)?
a) 4.19 × 10⁻³ S cm⁻¹
b) 2.38 × 10⁻³ S cm⁻¹
c) 1.84 × 10⁻³ S cm⁻¹
d) 3.67 × 10⁻³ S cm⁻¹
Answer: a) 4.19 × 10⁻³ S cm⁻¹
Explanation:
κ = Cell constant/R = 0.88 cm⁻¹ / 210 Ω = 4.19 × 10⁻³ S cm⁻¹
54. For Cu²⁺ + 2e⁻ → Cu, E° = +0.34 V and for Zn²⁺ + 2e⁻ → Zn, E° = -0.76 V. What will be the standard EMF of the Daniell cell?
a) 0.42 V
b) 1.10 V
c) -1.10 V
d) -0.42 V
Answer: b) 1.10 V
Explanation:
E°cell = E°cathode – E°anode = 0.34 – (-0.76) = 1.10 V
55. What amount of Ag will be liberated at the cathode when a current of 2A is passed for 30 minutes? (Atomic weight of Ag = 108, F = 96500 C mol⁻¹)
a) 2.01 g
b) 4.03 g
c) 6.72 g
d) 8.06 g
Answer: b) 4.03 g
Explanation:
m = ZIt = (108/96500) × 2 × (30×60) = 4.03 g
56. The resistance of 0.02 M KCl solution at 298 K was measured as 300 Ω. If its molar conductivity is 138.3 S cm² mol⁻¹, what will be the cell constant?
a) 0.5 cm⁻¹
b) 0.83 cm⁻¹
c) 1.2 cm⁻¹
d) 1.5 cm⁻¹
Answer: b) 0.83 cm⁻¹
Explanation:
Λₘ = (κ × 1000)/M ⇒ κ = (Λₘ × M)/1000 = (138.3 × 0.02)/1000 = 2.766 × 10⁻³ S cm⁻¹
Cell constant = κ × R = 2.766 × 10⁻³ × 300 = 0.83 cm⁻¹
57. In an electrolytic cell, a current of 3A is passed for 2 hours. What will be the quantity of electricity (Charge) passed?
a) 21600 C
b) 10800 C
c) 32400 C
d) 64800 C
Answer: a) 21600 C
Explanation:
Q = I × t = 3 × (2 × 3600) = 21600 C
58. The molar conductivity of 0.1 M CH₃COOH is 5.2 S cm² mol⁻¹. What will be its degree of dissociation? (Given: Λ°ₘ(CH₃COOH) = 390.7 S cm² mol⁻¹)
a) 0.0133
b) 0.0266
c) 0.052
d) 0.104
Answer: a) 0.0133
Explanation:
α = Λₘ/Λ°ₘ = 5.2/390.7 = 0.0133
59. In an electrolytic cell, when a current of 2A is passed for 1 hour, 2.42 g of Cu is deposited at the cathode. What is the electrochemical equivalent of Cu?
a) 0.000336 g/C
b) 0.000672 g/C
c) 0.001344 g/C
d) 0.002688 g/C
Answer: b) 0.000672 g/C
Explanation:
Z = m/(I×t) = 2.42/(2 × 3600) = 0.000336 g/C
60. The molar conductivity of 0.05 M NaOH solution is 250 S cm² mol⁻¹. What will be its specific conductance?
a) 0.0125 S cm⁻¹
b) 0.025 S cm⁻¹
c) 0.005 S cm⁻¹
d) 0.05 S cm⁻¹
Answer: a) 0.0125 S cm⁻¹
Explanation:
κ = (Λₘ × M)/1000 = (250 × 0.05)/1000 = 0.0125 S cm⁻¹
61. For a cell reaction with n=3 and E°cell = 0.15 V, what will be the equilibrium constant at 298 K? (R=8.314 J K⁻¹ mol⁻¹, F=96500 C mol⁻¹)
a) 1.2 × 10⁷
b) 2.4 × 10⁷
c) 1.8 × 10⁷
d) 3.6 × 10⁷
Answer: a) 1.2 × 10⁷
Explanation:
log K = (nE°)/0.0591 = (3 × 0.15)/0.0591 = 7.614 ⇒ K = 10^7.614 ≈ 1.2 × 10⁷
62. The resistance of 0.1 M HCl solution was measured as 50 Ω. If the cell constant is 1.15 cm⁻¹, what will be the molar conductivity?
a) 230 S cm² mol⁻¹
b) 460 S cm² mol⁻¹
c) 115 S cm² mol⁻¹
d) 57.5 S cm² mol⁻¹
Answer: a) 230 S cm² mol⁻¹
Explanation:
κ = Cell constant/R = 1.15/50 = 0.023 S cm⁻¹
Λₘ = (κ × 1000)/M = (0.023 × 1000)/0.1 = 230 S cm² mol⁻¹
63. The molar conductivity of 0.01 M CH₃COOH solution is 16.5 S cm² mol⁻¹. If Λ°ₘ = 390.7 S cm² mol⁻¹, what will be the dissociation constant (Ka)?
a) 1.8 × 10⁻⁵
b) 1.8 × 10⁻⁴
c) 1.8 × 10⁻³
d) 1.8 × 10⁻²
Answer: a) 1.8 × 10⁻⁵
Explanation:
α = Λₘ/Λ°ₘ = 16.5/390.7 = 0.0422
Ka = Cα² = 0.01 × (0.0422)² = 1.8 × 10⁻⁵
64. The resistance of 0.02 M NaCl solution at 298 K is 200 Ω. If the cell constant is 1.0 cm⁻¹, what will be the molar conductivity?
a) 250 S cm² mol⁻¹
b) 125 S cm² mol⁻¹
c) 500 S cm² mol⁻¹
d) 100 S cm² mol⁻¹
Answer: a) 250 S cm² mol⁻¹
Explanation:
κ = 1/200 = 0.005 S cm⁻¹
Λₘ = (0.005 × 1000)/0.02 = 250 S cm² mol⁻¹
65. The molar conductivity of 0.1 M NH₄OH is 10 S cm² mol⁻¹. If Λ°ₘ = 250 S cm² mol⁻¹, what will be the degree of dissociation (α)?
a) 0.02
b) 0.04
c) 0.06
d) 0.08
Answer: b) 0.04
Explanation:
α = Λₘ/Λ°ₘ = 10/250 = 0.04
66. The equivalent conductivity of 0.05 M BaCl₂ solution is 120 S cm² equiv⁻¹. What will be its molar conductivity?
a) 60 S cm² mol⁻¹
b) 120 S cm² mol⁻¹
c) 240 S cm² mol⁻¹
d) 480 S cm² mol⁻¹
Answer: c) 240 S cm² mol⁻¹
Explanation:
Λₘ = Λ_eq × n-factor = 120 × 2 = 240 S cm² mol⁻¹
67. In an electrolytic cell, when a current of 5A is passed for 30 minutes, 3.04 g of metal is deposited at the cathode. What is the equivalent weight of the metal? (F = 96500 C mol⁻¹)
a) 31.75
b) 63.5
c) 127
d) 254
Answer: b) 63.5
Explanation:
W = (E × I × t)/96500 ⇒ E = (W × 96500)/(I × t) = (3.04 × 96500)/(5 × 1800) = 63.5
68. The dissociation constant of 0.1 M CH₃COOH is 1.8 × 10⁻⁵. What will be its molar conductivity? (Λ°ₘ = 390.7 S cm² mol⁻¹)
a) 5.25 S cm² mol⁻¹
b) 16.6 S cm² mol⁻¹
c) 52.5 S cm² mol⁻¹
d) 166 S cm² mol⁻¹
Answer: b) 16.6 S cm² mol⁻¹
Explanation:
α = √(Ka/C) = √(1.8×10⁻⁵/0.1) = 0.0134
Λₘ = Λ°ₘ × α = 390.7 × 0.0134 = 16.6 S cm² mol⁻¹
69. The specific conductance of 0.01 M KCl solution at 298 K is 0.141 S m⁻¹. If its resistance is measured as 85 Ω, what will be the cell constant?
a) 12 cm⁻¹
b) 1.2 cm⁻¹
c) 0.12 cm⁻¹
d) 0.012 cm⁻¹
Answer: a) 12 cm⁻¹
Explanation:
κ = 0.141 S m⁻¹ = 0.00141 S cm⁻¹
Cell constant = κ × R = 0.00141 × 85 × 100 = 12 cm⁻¹
70. What will be the ratio of conductivities of 0.1 M HCl and 0.1 M CH₃COOH solutions? (Given: Λₘ(HCl) = 420 S cm² mol⁻¹, Λₘ(CH3COOH) = 5.2 S cm² mol⁻¹)
a) 1:1
b) 21:1
c) 42:1
d) 80:1
Answer: d) 80:1
Explanation:
Conductivity ratio = Λₘ(HCl)/Λₘ(CH₃COOH) = 420/5.2 ≈ 80:1
71. The resistance of 0.01 M NaCl solution is 100 Ω. If the cell constant is 0.5 cm⁻¹, what will be the specific conductance?
a) 0.005 S cm⁻¹
b) 0.01 S cm⁻¹
c) 0.02 S cm⁻¹
d) 0.05 S cm⁻¹
Answer: a) 0.005 S cm⁻¹
Explanation:
κ = Cell constant/R = 0.5/100 = 0.005 S cm⁻¹
72. The molar conductivity of 0.02 M CuSO₄ solution is 100 S cm² mol⁻¹. What will be its specific conductance?
a) 0.002 S cm⁻¹
b) 0.005 S cm⁻¹
c) 0.01 S cm⁻¹
d) 0.02 S cm⁻¹
Answer: a) 0.002 S cm⁻¹
Explanation:
κ = (Λₘ × M)/1000 = (100 × 0.02)/1000 = 0.002 S cm⁻¹
73. The molar conductivity of 0.1 M NaOH solution is 250 S cm² mol⁻¹. If Λ°ₘ = 250 S cm² mol⁻¹, what will be the degree of dissociation (α)?
a) 0.5
b) 1.0
c) 0.25
d) 0.75
Answer: b) 1.0
Explanation:
α = Λₘ/Λ°ₘ = 250/250 = 1.0 (Strong electrolyte)
74. The equivalent conductivity of 0.05 M CaCl₂ solution is 120 S cm² equiv⁻¹. What will be its specific conductance?
a) 0.006 S cm⁻¹
b) 0.012 S cm⁻¹
c) 0.024 S cm⁻¹
d) 0.048 S cm⁻¹
Answer: a) 0.006 S cm⁻¹
Explanation:
Λ_eq = (κ × 1000)/N ⇒ κ = (Λ_eq × N)/1000 = (120 × 0.1)/1000 = 0.012 S cm⁻¹
(Here N = 2 × 0.05 = 0.1, since n=2 for CaCl₂)
75. The dissociation constant of 0.1 M CH₃COOH is 1.8 × 10⁻⁵. If Λ°ₘ = 390.7 S cm² mol⁻¹, what will be its equivalent conductivity?
a) 8.3 S cm² equiv⁻¹
b) 16.6 S cm² equiv⁻¹
c) 33.2 S cm² equiv⁻¹
d) 66.4 S cm² equiv⁻¹
Answer: b) 16.6 S cm² equiv⁻¹
Explanation:
α = √(Ka/C) = √(1.8×10⁻⁵/0.1) = 0.0134
Λₘ = Λ°ₘ × α = 390.7 × 0.0134 = 16.6 S cm² mol⁻¹
Λ_eq = Λₘ/n-factor = 16.6/1 = 16.6 S cm² equiv⁻¹ (n=1 for CH3COOH)
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