31. Which of the following statements about a concentration cell is true?
- a) It has identical electrodes and electrolytes but different concentrations
- b) It operates on a temperature difference between the two half-cells
- c) It produces electrical energy through fuel combustion
- d) The cell potential is always zero
Answer: a) It has identical electrodes and electrolytes but different concentrations
Explanation: A concentration cell consists of two half-cells with the same electrodes and electrolytes, but different ion concentrations. The cell potential arises due to this concentration difference.
32. Which substance is typically used as the electrolyte in a nickel-cadmium battery?
- a) Sulfuric acid
- b) Potassium hydroxide
- c) Ammonium chloride
- d) Sodium chloride
Answer: b) Potassium hydroxide
Explanation: Nickel-cadmium batteries use an alkaline electrolyte, typically potassium hydroxide (KOH), to facilitate the electrochemical reactions.
33. Which of the following metals will NOT corrode in moist air?
- a) Zinc
- b) Aluminum
- c) Gold
- d) Iron
Answer: c) Gold
Explanation: Gold is highly resistant to corrosion due to its very low reactivity, making it one of the least reactive metals in air or water.
34. In the electrolysis of water, which gas is produced at the anode?
- a) Hydrogen
- b) Oxygen
- c) Chlorine
- d) Nitrogen
Answer: b) Oxygen
Explanation: During the electrolysis of water, oxygen gas is produced at the anode due to the oxidation of water molecules (2H₂O → O₂ + 4H⁺ + 4e⁻).
35. The electrode potential of the standard hydrogen electrode (SHE) is:
- a) 1V
- b) 0V
- c) -1V
- d) +1.5V
Answer: b) 0V
Explanation: The standard hydrogen electrode (SHE) is defined to have an electrode potential of exactly 0V, and it serves as the reference for measuring the potentials of other electrodes.
36. Corrosion of metals is an example of:
- a) Oxidation reaction
- b) Reduction reaction
- c) Decomposition reaction
- d) Acid-base reaction
Answer: a) Oxidation reaction
Explanation: Corrosion occurs when a metal is oxidized, losing electrons and reacting with environmental agents like oxygen and moisture.
37. The cathode material used in a lithium-ion battery is typically:
- a) Nickel
- b) Graphite
- c) Lithium cobalt oxide
- d) Lead dioxide
Answer: c) Lithium cobalt oxide
Explanation: In most lithium-ion batteries, lithium cobalt oxide (LiCoO₂) is used as the cathode material, providing high energy density.
38. The direction of current in an electrolytic cell is:
- a) From cathode to anode in the external circuit
- b) From anode to cathode in the external circuit
- c) From electrolyte to the electrodes
- d) From the salt bridge to the electrodes
Answer: b) From anode to cathode in the external circuit
Explanation: In an electrolytic cell, current flows from the positive anode to the negative cathode in the external circuit.
39. Which metal is commonly used for galvanizing iron to prevent corrosion?
- a) Zinc
- b) Aluminum
- c) Copper
- d) Lead
Answer: a) Zinc
Explanation: Zinc is commonly used to coat iron in the galvanization process, protecting the iron from rusting by acting as a sacrificial anode.
40. In a fuel cell, which of the following is consumed as a fuel?
- a) Oxygen
- b) Hydrogen
- c) Methane
- d) Water
Answer: b) Hydrogen
Explanation: In a hydrogen fuel cell, hydrogen is the primary fuel that reacts with oxygen to generate electricity, with water as the byproduct.
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