MCAT General Chemistry Question 243: Answer and Explanation

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Question: 243

5. Which of the following best describes the difference between a galvanic cell and an electrolytic cell?

  • A. In a galvanic cell, the anode is the site of oxidation, whereas in an electrolytic cell the anode is the site of reduction.
  • B. In a galvanic cell, the cathode is the negative electrode, whereas in an electrolytic cell the cathode is the positive electrode.
  • C. In a galvanic cell, spontaneous reactions generate a current, whereas in an electrolytic cell a current forces nonspontaneous reactions to occur.
  • D. In a galvanic cell, the electrons flow from anode to cathode, whereas in an electrolytic cell the electrons flow from cathode to anode.

Correct Answer: C

Explanation:

C The anode is always the site of oxidation and the cathode is always the site of reduction; therefore, electrons always flow from the anode (oxidation) to the cathode (reduction) regardless of the kind of cell (choices A and D are wrong). In a galvanic cell, a spontaneous reaction liberates electrons and they flow freely to the positive electrode, which in this case would be the cathode. However, in an electrolytic cell the current is forcing the electrons to flow where they don't want to go: the negative electrode. In this case the cathode would be the negative electrode (choice B is wrong).

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