Electrochemistry Important Mcqs FPSC Lecturer Chemistry Test

1. In the reaction Cl₂ → 2Cl⁻, chlorine is:
a) Oxidized
b) Reduced
c) Neither
d) Both
Answer: b) Reduced

2. The mnemonic “OIL RIG” stands for:
a) Oxidation Is Loss, Reduction Is Gain
b) Oxidation Is Gain, Reduction Is Loss
c) Oxidation Increases Charge, Reduction Decreases Charge
d) None of these
Answer: a) Oxidation Is Loss, Reduction Is Gain

3. In the reaction Na → Na⁺, sodium is:
a) Oxidized
b) Reduced
c) A reducing agent
d) Both a and c
Answer: d) Both a and c

4. The reducing agent in a redox reaction:
a) Gains electrons
b) Loses electrons
c) Is reduced
d) Is always a metal
Answer: b) Loses electrons

5. What is the oxidation number of oxygen in H₂O₂?
a) -2
b) -1
c) +1
d) 0
Answer: b) -1

6. The oxidation number of Al in Al₂O₃ is:
a) +2
b) +3
c) -3
d) +1
Answer: b) +3

7. In Na₂SO₃, the oxidation state of sulfur is:
a) +4
b) +6
c) -2
d) 0
Answer: a) +4

8. Hydrogen has an oxidation state of -1 in:
a) H₂O
b) CH₄
c) NaH
d) HCl
Answer: c) NaH

9. Which element is reduced in the reaction: 2H₂ + O₂ → 2H₂O?
a) H₂
b) O₂
c) Both
d) Neither
Answer: b) O₂

10. The oxidation number of Cr in Cr₂O₇²⁻ is:
a) +3
b) +6
c) +2
d) -2
Answer: b) +6

11. In molten KI electrolysis, the product at the anode is:
a) K
b) I₂
c) H₂
d) O₂
Answer: b) I₂

12. During aqueous electrolysis of KI, the cathode product is:
a) K
b) H₂
c) I₂
d) O₂
Answer: b) H₂

13. Electrolysis is used for:
a) Recharging batteries
b) Electroplating
c) Both a and b
d) None
Answer: c) Both a and b

14. In molten NaCl electrolysis, the anode reaction is:
a) 2Cl⁻ → Cl₂ + 2e⁻
b) Na⁺ + e⁻ → Na
c) H₂O → O₂ + H⁺
d) None
Answer: a) 2Cl⁻ → Cl₂ + 2e⁻

15. The purpose of a salt bridge is to:
a) Transfer electrons
b) Maintain electrical neutrality
c) Increase voltage
d) Reduce resistance
Answer: b) Maintain electrical neutrality

16. In a galvanic cell, electrons flow from:
a) Anode to cathode
b) Cathode to anode
c) Salt bridge to anode
d) Salt bridge to cathode
Answer: a) Anode to cathode

17. The cathode in a galvanic cell is the site of:
a) Oxidation
b) Reduction
c) Neutralization
d) Hydrolysis
Answer: b) Reduction

18. Which metal is the anode in a Zn-Cu galvanic cell?
a) Zn
b) Cu
c) Both
d) Salt bridge
Answer: a) Zn

19. The standard hydrogen electrode (SHE) has a potential of:
a) 0.00 V
b) 1.00 V
c) -1.00 V
d) 2.00 V
Answer: a) 0.00 V

20. If E°cell is positive, the reaction is:
a) Spontaneous
b) Non-spontaneous
c) At equilibrium
d) None
Answer: a) Spontaneous

21. The strongest oxidizing agent is:
a) K⁺
b) Ag⁺
c) Zn²⁺
d) Fe²⁺
Answer: b) Ag⁺

22. The strongest reducing agent is:
a) K
b) Ag
c) Zn
d) Fe
Answer: a) K

23. E°cell for Zn + Cu²⁺ → Zn²⁺ + Cu is:
(Given: E°(Zn²⁺/Zn) = -0.76 V; E°(Cu²⁺/Cu) = +0.34 V)
a) -1.10 V
b) +1.10 V
c) +0.42 V
d) -0.42 V
Answer: b) +1.10 V

24. A negative E°cell indicates:
a) Spontaneous reaction
b) Non-spontaneous reaction
c) No reaction
d) Equilibrium
Answer: b) Non-spontaneous reaction

25. Which pair will react spontaneously?
a) Ag⁺ and Cu
b) Zn²⁺ and Fe
c) K⁺ and Na
d) None
Answer: a) Ag⁺ and Cu

26. The Nernst equation is used to calculate:
a) E°cell
b) Ecell under non-standard conditions
c) ΔG
d) Reaction quotient
Answer: b) Ecell under non-standard conditions

27. If [Cu²⁺] increases in Zn + Cu²⁺ → Zn²⁺ + Cu, Ecell:
a) Increases
b) Decreases
c) Remains same
d) Becomes zero
Answer: a) Increases

28. For the reaction 2Cr + 6H⁺ → 3H₂ + 2Cr³⁺, E°cell is:
(Given: E°(Cr³⁺/Cr) = -0.74 V; E°(H⁺/H₂) = 0.00 V)
a) +0.74 V
b) -0.74 V
c) +1.48 V
d) -1.48 V
Answer: a) +0.74 V

29. The term (0.0592/n) in the Nernst equation is valid at:
a) 0°C
b) 25°C
c) 100°C
d) Any temperature
Answer: b) 25°C

30. If Q = 1, then Ecell =
a) 0
b) E°cell
c) 0.0592
d) None
Answer: b) E°cell

31. Faraday’s constant is approximately:
a) 96,500 C/mol
b) 6.02 × 10²³ C/mol
c) 8.314 J/mol·K
d) 1.602 × 10⁻¹⁹ C
Answer: a) 96,500 C/mol

32. A current of 2A flows for 1 hour. Total charge is:
a) 2 C
b) 7200 C
c) 3600 C
d) 1.6 × 10⁻¹⁹ C
Answer: b) 7200 C

33. To deposit 1 mole of Ag (atomic wt. 108 g/mol) from Ag⁺, required charge is:
a) 1 F
b) 2 F
c) 3 F
d) 0.5 F
Answer: a) 1 F

34. Electroplating uses:
a) Galvanic cells
b) Electrolytic cells
c) Both
d) None
Answer: b) Electrolytic cells

35. Time to deposit 10g of Cu (At. wt. 63.5) using 5A current:
(Cu²⁺ + 2e⁻ → Cu)
a) 6077 s
b) 3038 s
c) 1519 s
d) 759 s
Answer: a) 6077 s

36. In an electrolytic cell, the anode is:
a) Positive
b) Negative
c) Neutral
d) None
Answer: a) Positive

37. The salt bridge contains:
a) Reactive ions
b) Unreactive ions
c) Only cations
d) Only anions
Answer: b) Unreactive ions

38. ΔG and Ecell are related by:
a) ΔG = -nFEcell
b) ΔG = nFEcell
c) ΔG = RT ln Ecell
d) None
Answer: a) ΔG = -nFEcell

39. Which is a polyatomic ion?
a) NH₄⁺
b) CO₃²⁻
c) SO₄²⁻
d) All
Answer: d) All

40. In HPO₃²⁻, the oxidation state of P is:
a) +3
b) +5
c) +4
d) +6
Answer: a) +3

41. In a galvanic cell, the anode is:
a) Where oxidation occurs
b) Where reduction occurs
c) Neutral
d) None
Answer: a) Where oxidation occurs

42. The formula for calculating E°cell is:
a) E°cell = E°cathode – E°anode
b) E°cell = E°anode – E°cathode
c) E°cell = E°cathode + E°anode
d) None
Answer: a) E°cell = E°cathode – E°anode

43. The oxidizing agent in the reaction Zn + Cu²⁺ → Zn²⁺ + Cu is:
a) Zn
b) Cu²⁺
c) Zn²⁺
d) Cu
Answer: b) Cu²⁺

44. In the reaction Fe²⁺ → Fe³⁺ + e⁻, iron is:
a) Oxidized
b) Reduced
c) Neither
d) Both
Answer: a) Oxidized

45. The oxidation state of Mn in MnO₄⁻ is:
a) +7
b) +6
c) +5
d) +4
Answer: a) +7

46. Which reaction represents reduction?
a) Cl₂ → 2Cl⁻
b) Fe²⁺ → Fe³⁺
c) Na → Na⁺
d) None
Answer: a) Cl₂ → 2Cl⁻

47. In the electrolysis of water, the ratio of H₂ to O₂ volume is:
a) 2:1
b) 1:2
c) 1:1
d) 3:1
Answer: a) 2:1

48. The oxidation state of N in NH₃ is:
a) -3
b) +3
c) 0
d) +5
Answer: a) -3

49. Which metal is most likely to corrode in moist air?
a) Iron
b) Gold
c) Platinum
d) Silver
Answer: a) Iron

50. Rusting of iron is an example of:
a) Oxidation
b) Reduction
c) Displacement
d) None
Answer: a) Oxidation

51. The cathode in an electrolytic cell is:
a) Positive
b) Negative
c) Neutral
d) None
Answer: b) Negative

52. Which is a non-spontaneous process?
a) Electrolysis
b) Galvanic cell reaction
c) Rusting
d) Combustion
Answer: a) Electrolysis

53. The oxidation state of S in H₂S is:
a) -2
b) +6
c) +4
d) 0
Answer: a) -2

54. The formula mass of KMnO₄ is:
a) 158 g/mol
b) 142 g/mol
c) 122 g/mol
d) 100 g/mol
Answer: a) 158 g/mol

55. In the reaction 2H₂O → 2H₂ + O₂, water acts as:
a) Electrolyte
b) Catalyst
c) Reducing agent
d) Oxidizing agent
Answer: a) Electrolyte

56. Which is a secondary cell?
a) Lead-acid battery
b) Dry cell
c) Fuel cell
d) All
Answer: a) Lead-acid battery

57. The electrolyte in a lead-acid battery is:
a) H₂SO₄
b) HCl
c) NaOH
d) NaCl
Answer: a) H₂SO₄

58. The oxidation state of C in CH₄ is:
a) -4
b) +4
c) 0
d) -1
Answer: a) -4

59. The oxidation state of O in OF₂ is:
a) +2
b) -2
c) 0
d) +1
Answer: a) +2

60. Which is a metalloid?
a) Silicon
b) Sodium
c) Chlorine
d) Iron
Answer: a) Silicon

61. The oxidation state of Fe in Fe₃O₄ is:
a) +8/3
b) +2
c) +3
d) +4
Answer: a) +8/3

62. In the reaction 2KClO₃ → 2KCl + 3O₂, the substance reduced is:
a) Cl
b) O
c) K
d) None
Answer: a) Cl

63. The oxidation state of N in NO₂⁻ is:
a) +3
b) +5
c) -3
d) +4
Answer: a) +3

64. In a concentration cell, the driving force is:
a) Difference in ion concentration
b) Temperature
c) Pressure
d) None
Answer: a) Difference in ion concentration

65. The Nernst equation accounts for:
a) Temperature
b) Concentration
c) Both
d) None
Answer: c) Both

66. The unit of electrical charge is:
a) Coulomb
b) Volt
c) Ohm
d) Ampere
Answer: a) Coulomb

67. Which ion is a common component of salt bridges?
a) K⁺
b) Ag⁺
c) Cl⁻
d) Both a and c
Answer: d) Both a and c

68. The oxidation state of Br in BrO₃⁻ is:
a) +5
b) -1
c) +3
d) +7
Answer: a) +5

69. The oxidation state of N in N₂O₅ is:
a) +5
b) +3
c) -3
d) 0
Answer: a) +5

70. Which metal is used in galvanization?
a) Zinc
b) Copper
c) Silver
d) Gold
Answer: a) Zinc

71. The process of coating iron with zinc is called:
a) Galvanization
b) Electroplating
c) Anodizing
d) None
Answer: a) Galvanization

72. Which reaction occurs at the cathode in a hydrogen fuel cell?
a) O₂ + 4H⁺ + 4e⁻ → 2H₂O
b) H₂ → 2H⁺ + 2e⁻
c) Both
d) None
Answer: a) O₂ + 4H⁺ + 4e⁻ → 2H₂O

73. The oxidation state of S in SO₃²⁻ is:
a) +4
b) +6
c) -2
d) 0
Answer: a) +4

74. Which is a primary cell?
a) Dry cell
b) Lead-acid battery
c) Fuel cell
d) All
Answer: a) Dry cell

75. The electrolyte in a dry cell is:
a) NH₄Cl
b) H₂SO₄
c) NaOH
d) NaCl
Answer: a) NH₄Cl

76. The oxidation state of Mn in MnO₂ is:
a) +4
b) +7
c) +2
d) +6
Answer: a) +4

77. Which metal is used as a sacrificial anode for iron?
a) Zinc
b) Copper
c) Silver
d) Gold
Answer: a) Zinc

78. The oxidation state of C in CO₃²⁻ is:
a) +4
b) -4
c) +2
d) 0
Answer: a) +4

79. The oxidation state of P in PO₄³⁻ is:
a) +5
b) +3
c) -3
d) 0
Answer: a) +5

80. The oxidation state of Cl in HClO₄ is:
a) +7
b) -1
c) +5
d) +3
Answer: a) +7

81. Which reaction is spontaneous?
a) Cu²⁺ + Zn → Zn²⁺ + Cu
b) Zn²⁺ + Cu → Cu²⁺ + Zn
c) Both
d) None
Answer: a) Cu²⁺ + Zn → Zn²⁺ + Cu

82. The oxidation state of O in O₂ is:
a) 0
b) -2
c) +1
d) -1
Answer: a) 0

83. The oxidation state of N in NH₄⁺ is:
a) -3
b) +5
c) +1
d) +3
Answer: a) -3

84. Which is a use of electrolysis?
a) Electroplating
b) Metal extraction
c) Both
d) None
Answer: c) Both

85. The oxidation state of S in H₂SO₃ is:
a) +4
b) +6
c) -2
d) 0
Answer: a) +4

86. The oxidation state of N in HNO₃ is:
a) +5
b) +3
c) -3
d) 0
Answer: a) +5

87. Which substance is the oxidizing agent in 2Fe + 3Cl₂ → 2FeCl₃?
a) Cl₂
b) Fe
c) FeCl₃
d) None
Answer: a) Cl₂

88. The oxidation state of Cr in CrO₄²⁻ is:
a) +6
b) +3
c) +2
d) -2
Answer: a) +6

89. The oxidation state of C in C₂H₄ is:
a) -2
b) +4
c) 0
d) -1
Answer: a) -2

90. The oxidation state of As in AsO₄³⁻ is:
a) +5
b) +3
c) -3
d) 0
Answer: a) +5

91. The oxidation state of N in N₂H₄ is:
a) -2
b) +2
c) -1
d) +1
Answer: a) -2

92. The oxidation state of S in S₈ is:
a) 0
b) -2
c) +6
d) +4
Answer: a) 0

93. The oxidation state of Cl in ClO⁻ is:
a) +1
b) -1
c) +3
d) +5
Answer: a) +1

94. The oxidation state of Mn in MnO₄²⁻ is:
a) +6
b) +7
c) +4
d) +2
Answer: a) +6

95. The oxidation state of C in CH₃OH is:
a) -2
b) +4
c) 0
d) -1
Answer: a) -2

96. The oxidation state of O in KO₂ is:
a) -½
b) -2
c) -1
d) +1
Answer: a) -½

97. The oxidation state of N in NO is:
a) +2
b) -3
c) +5
d) 0
Answer: a) +2

98. The oxidation state of Fe in Fe(CO)₅ is:
a) 0
b) +2
c) +3
d) -2
Answer: a) 0

99. The oxidation state of B in NaBH₄ is:
a) +3
b) -3
c) +5
d) 0
Answer: a) +3

100. The oxidation state of U in UO₂²⁺ is:
a) +6
b) +4
c) +2
d) 0
Answer: a) +6