61. In a hydrogen-oxygen fuel cell, the overall reaction is:
- a) 2H₂ + O₂ → 2H₂O
- b) 2H₂ + O₂ → H₂O₂
- c) H₂O → H₂ + O₂
- d) H₂ + O₂ → H₂O
Answer: a) 2H₂ + O₂ → 2H₂O
Explanation: In a hydrogen-oxygen fuel cell, hydrogen reacts with oxygen to form water, producing electrical energy.
62. In an electrochemical cell, the salt bridge:
- a) Allows for the transfer of electrons
- b) Completes the electrical circuit by allowing ions to flow
- c) Provides the voltage difference
- d) Provides a solid electrolyte
Answer: b) Completes the electrical circuit by allowing ions to flow
Explanation: The salt bridge allows the movement of ions to maintain charge neutrality and completes the electrical circuit in an electrochemical cell.
63. Which of the following ions migrates towards the anode during the electrolysis of an aqueous NaCl solution?
- a) Na⁺
- b) Cl⁻
- c) OH⁻
- d) H⁺
Answer: b) Cl⁻
Explanation: During the electrolysis of aqueous NaCl, chloride ions (Cl⁻) migrate towards the anode, where they are oxidized to form chlorine gas.
64. In the electrolysis of water, what is the ratio of hydrogen to oxygen gases produced?
- a) 1:1
- b) 2:1
- c) 1:2
- d) 3:2
Answer: b) 2:1
Explanation: The electrolysis of water produces hydrogen and oxygen gases in a 2:1 ratio (2H₂O → 2H₂ + O₂).
65. In an electrochemical cell, the anode is the site of:
- a) Oxidation
- b) Reduction
- c) Electron gain
- d) Salt bridge formation
Answer: a) Oxidation
Explanation: In an electrochemical cell, oxidation (loss of electrons) occurs at the anode.
66. Which metal is deposited at the cathode during the electrolysis of copper(II) sulfate solution using copper electrodes?
- a) Zinc
- b) Copper
- c) Silver
- d) Iron
Answer: b) Copper
Explanation: During the electrolysis of copper(II) sulfate solution with copper electrodes, copper ions are reduced and deposited at the cathode.
67. The electrode where reduction occurs in an electrochemical cell is called:
- a) Cathode
- b) Anode
- c) Electrolyte
- d) Salt bridge
Answer: a) Cathode
Explanation: Reduction (gain of electrons) occurs at the cathode in both galvanic and electrolytic cells.
68. The relationship between Gibbs free energy (ΔG) and cell potential (E) is given by:
- a) ΔG = nFE
- b) ΔG = -nFE
- c) ΔG = -E/nF
- d) ΔG = E/nF
Answer: b) ΔG = -nFE
Explanation: The relationship between Gibbs free energy and cell potential is ΔG = -nFE, where n is the number of moles of electrons, F is Faraday’s constant, and E is the cell potential.
71. In a galvanic cell, the salt bridge contains:
- a) A solution of strong acids
- b) A solution of electrolytes
- c) A solution of reducing agents
- d) Pure water
Answer: b) A solution of electrolytes
Explanation: The salt bridge in a galvanic cell contains an electrolyte solution (usually KCl or NaCl) that helps maintain charge neutrality by allowing the flow of ions.
72. The electrolysis of molten aluminum oxide involves the use of:
- a) Copper electrodes
- b) Iron electrodes
- c) Graphite electrodes
- d) Silver electrodes
Answer: c) Graphite electrodes
Explanation: In the electrolysis of molten aluminum oxide (Al₂O₃), graphite electrodes are used due to their ability to withstand high temperatures and act as an inert conductor.
73. Which of the following is the main advantage of a fuel cell over a conventional battery?
- a) Higher voltage output
- b) Continuous energy supply as long as fuel is provided
- c) Faster rate of chemical reactions
- d) Cheaper to produce
Answer: b) Continuous energy supply as long as fuel is provided
Explanation: Fuel cells can continuously generate electricity as long as fuel (such as hydrogen) and an oxidizing agent (such as oxygen) are supplied, unlike batteries, which store a fixed amount of energy.
74. Which of the following metals is the best reducing agent according to the electrochemical series?
- a) Lithium
- b) Sodium
- c) Zinc
- d) Copper
Answer: a) Lithium
Explanation: Lithium has the most negative standard reduction potential in the electrochemical series, making it the strongest reducing agent.
75. Which electrolyte is used in a molten carbonate fuel cell (MCFC)?
- a) Potassium hydroxide
- b) Sodium chloride
- c) Molten lithium carbonate
- d) Sulfuric acid
Answer: c) Molten lithium carbonate
Explanation: In a molten carbonate fuel cell (MCFC), molten lithium carbonate is used as the electrolyte, allowing for high-temperature operation.
76. Which of the following processes leads to the protection of metals by the formation of a thin oxide layer?
- a) Cathodic protection
- b) Galvanizing
- c) Anodizing
- d) Electroplating
Answer: c) Anodizing
Explanation: Anodizing is a process that increases the thickness of the natural oxide layer on the surface of metals like aluminum, providing corrosion resistance.
77. Which of the following elements is used as a cathode material in a standard hydrogen electrode (SHE)?
- a) Platinum
- b) Gold
- c) Copper
- d) Silver
Answer: a) Platinum
Explanation: Platinum is used as the inert cathode material in a standard hydrogen electrode (SHE) because it facilitates the exchange of electrons without reacting with hydrogen gas.
78. Which of the following is used as a reducing agent in a blast furnace during iron extraction?
- a) Oxygen
- b) Carbon monoxide
- c) Carbon dioxide
- d) Hydrogen
Answer: b) Carbon monoxide
Explanation: In the blast furnace, carbon monoxide acts as the reducing agent that reduces iron ore (Fe₂O₃) to metallic iron (Fe).
79. The electrochemical cell in which both electrodes are made of the same material but differ in ion concentration is known as:
- a) A galvanic cell
- b) An electrolytic cell
- c) A concentration cell
- d) A fuel cell
Answer: c) A concentration cell
Explanation: In a concentration cell, the electrodes are the same, but the ion concentrations in the electrolytes differ, creating a potential difference.
80. In a galvanic cell, the positive terminal is the:
- a) Cathode
- b) Anode
- c) Salt bridge
- d) Electrolyte
Answer: a) Cathode
Explanation: In a galvanic cell, the cathode is the positive terminal because it attracts electrons, and reduction occurs at this electrode.
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