51. Which of the following is a secondary cell?
- a) Zinc-carbon cell
- b) Lead-acid battery
- c) Silver oxide battery
- d) Mercury cell
Answer: b) Lead-acid battery
Explanation: A secondary cell is rechargeable, and a lead-acid battery can be recharged by reversing the chemical reactions that occur during discharge.
52. In a galvanic cell, the oxidation half-reaction occurs at:
- a) The cathode
- b) The anode
- c) The salt bridge
- d) Both electrodes
Answer: b) The anode
Explanation: In a galvanic cell, oxidation (loss of electrons) occurs at the anode, which is negatively charged.
53. A Daniel cell can be represented as:
- a) Zn | Zn²⁺ || Cu²⁺ | Cu
- b) Cu | Cu²⁺ || Zn²⁺ | Zn
- c) Zn | Cu || Zn²⁺ | Cu²⁺
- d) Cu²⁺ | Cu || Zn²⁺ | Zn
Answer: a) Zn | Zn²⁺ || Cu²⁺ | Cu
Explanation: The anode (Zn) is on the left and the cathode (Cu) is on the right, separated by a salt bridge represented by the double vertical lines.
54. The overall reaction for a lead-acid storage battery during discharge is:
- a) Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O
- b) PbSO₄ + H₂O → Pb + H₂SO₄
- c) Pb + PbSO₄ → 2PbSO₄
- d) Pb + H₂SO₄ → PbO₂ + Pb
Answer: a) Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O
Explanation: During discharge, lead and lead dioxide react with sulfuric acid to form lead sulfate and water, releasing electrical energy.
55. In an electrochemical series, metals with a higher negative reduction potential:
- a) Are more easily oxidized
- b) Are more easily reduced
- c) Do not undergo reactions
- d) Have a lower tendency to lose electrons
Answer: a) Are more easily oxidized
Explanation: Metals with more negative reduction potentials are more likely to lose electrons and undergo oxidation.
56. Which of the following reactions occurs at the cathode in a lead-acid battery during discharge?
- a) PbO₂ + 4H⁺ + SO₄²⁻ + 2e⁻ → PbSO₄ + 2H₂O
- b) Pb → Pb²⁺ + 2e⁻
- c) 2H₂O → O₂ + 4H⁺ + 4e⁻
- d) PbSO₄ + 2H₂O → Pb + H₂SO₄
Answer: a) PbO₂ + 4H⁺ + SO₄²⁻ + 2e⁻ → PbSO₄ + 2H₂O
Explanation: In a lead-acid battery, lead dioxide (PbO₂) is reduced to lead sulfate (PbSO₄) at the cathode during discharge.
57. Which statement is true for the corrosion of iron?
- a) Oxidation occurs at the anode
- b) Oxidation occurs at the cathode
- c) The iron metal acts as a cathode
- d) The corrosion process does not involve any electron transfer
Answer: a) Oxidation occurs at the anode
Explanation: In the corrosion of iron, iron is oxidized to Fe²⁺ at the anode, while oxygen is reduced at the cathode.
58. The unit of cell potential is:
- a) Ohm
- b) Ampere
- c) Volt
- d) Coulomb
Answer: c) Volt
Explanation: The unit of cell potential (or electromotive force, EMF) is the volt, which represents the potential difference between the two electrodes.
59. What is the product at the cathode during the electrolysis of molten NaCl?
- a) Sodium
- b) Chlorine
- c) Oxygen
- d) Hydrogen
Answer: a) Sodium
Explanation: During the electrolysis of molten sodium chloride (NaCl), sodium metal is produced at the cathode.
60. The standard cell potential for a reaction can be calculated using:
- a) Nernst equation
- b) Gibbs free energy equation
- c) Faraday’s laws of electrolysis
- d) The standard reduction potentials of the half-reactions
Answer: d) The standard reduction potentials of the half-reactions
Explanation: The standard cell potential is calculated as the difference between the standard reduction potentials of the cathode and anode half-reactions.
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