21. Which of the following metals has the highest tendency to be oxidized?
- a) Copper
- b) Zinc
- c) Gold
- d) Silver
Answer: b) Zinc
Explanation: Zinc has a more negative standard electrode potential than copper, gold, or silver, which means it is more easily oxidized.
22. Which of the following statements is true for an electrolytic cell?
- a) The anode is positive and oxidation occurs there
- b) The cathode is positive and reduction occurs there
- c) The anode is negative and oxidation occurs there
- d) The cathode is positive and oxidation occurs there
Answer: a) The anode is positive and oxidation occurs there
Explanation: In an electrolytic cell, the anode is positive because the external source forces oxidation to occur at that electrode.
23. The cell notation for a galvanic cell is written as:
- a) Anode | electrolyte || cathode | electrolyte
- b) Cathode | electrolyte || anode | electrolyte
- c) Electrolyte | cathode || electrolyte | anode
- d) None of the above
Answer: a) Anode | electrolyte || cathode | electrolyte
Explanation: In cell notation, the anode and its electrolyte are written on the left, and the cathode and its electrolyte are written on the right, with a double vertical line (||) representing the salt bridge.
24. Electrolysis of molten NaCl produces:
- a) Sodium metal and chlorine gas
- b) Sodium metal and oxygen gas
- c) Sodium hydroxide and chlorine gas
- d) Sodium chloride and hydrogen gas
Answer: a) Sodium metal and chlorine gas
Explanation: During the electrolysis of molten NaCl, sodium metal is formed at the cathode, and chlorine gas is produced at the anode.
25. The main difference between a galvanic and electrolytic cell is that:
- a) A galvanic cell generates electrical energy, while an electrolytic cell requires electrical energy to function
- b) A galvanic cell operates under non-spontaneous conditions, while an electrolytic cell operates spontaneously
- c) Both cells require an external power source to function
- d) In both cells, the anode is positive
Answer: a) A galvanic cell generates electrical energy, while an electrolytic cell requires electrical energy to function
Explanation: A galvanic cell converts chemical energy into electrical energy spontaneously, while an electrolytic cell requires external electrical energy to drive a non-spontaneous reaction.
26. The voltage of a galvanic cell is called:
- a) Electromotive force (EMF)
- b) Current
- c) Resistance
- d) Power
Answer: a) Electromotive force (EMF)
Explanation: The voltage of a galvanic cell is known as its electromotive force (EMF), which is the potential difference between the two electrodes when no current is flowing.
27. The Nernst equation is used to calculate:
- a) The cell potential under non-standard conditions
- b) The resistance of the cell
- c) The current flowing through the cell
- d) The concentration of electrolytes
Answer: a) The cell potential under non-standard conditions
Explanation: The Nernst equation relates the cell potential to the standard electrode potential, temperature, and the concentrations of the reactants and products.
28. Which of the following factors affects the electrode potential of a half-cell?
- a) Temperature
- b) Concentration of ions
- c) Nature of the electrode
- d) All of the above
Answer: d) All of the above
Explanation: The electrode potential of a half-cell is influenced by temperature, concentration of the ions in the solution, and the material of the electrode.
29. The half-cell reaction at the cathode in a hydrogen fuel cell is:
- a) 2H₂ → 4H⁺ + 4e⁻
- b) O₂ + 4H⁺ + 4e⁻ → 2H₂O
- c) O₂ + 2H⁺ → H₂O₂
- d) H₂ → 2H⁺ + 2e⁻
Answer: b) O₂ + 4H⁺ + 4e⁻ → 2H₂O
Explanation: In a hydrogen fuel cell, oxygen is reduced at the cathode, combining with protons (H⁺) and electrons to form water.
30. What happens to the mass of the anode in a galvanic cell during operation?
- a) It decreases
- b) It increases
- c) It remains constant
- d) It depends on the electrolyte
Answer: a) It decreases
Explanation: In a galvanic cell, the anode undergoes oxidation, meaning the metal loses electrons and dissolves into the electrolyte, leading to a decrease in mass.
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