MCAT General Chemistry Question 179: Answer and Explanation

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Question: 179

14. Which of the following is the best explanation for the fact that a larger mass of electrodes are required for lead–acid batteries, as compared to other batteries, to produce a certain current?

  • A. The lead–acid electrolyte, sulfuric acid, is diprotic and incompletely dissociates in solution.
  • B. The energy density of lead–acid electrodes is higher than that of other batteries.
  • C. The electrolytes in other batteries less readily dissociate than those of lead–acid batteries.
  • D. The energy density of lead–acid electrodes is lower than that of other batteries.

Correct Answer: D

Explanation:

Compared to other cell types, lead-acid batteries have a characteristically low energy density, choice (D). While choice (A) is a true statement, the incomplete dissociation of sulfuric acid does not fully explain the low energy density of lead-acid batteries. Choice (C) is likely to be an opposite; the more easily the electrodes dissociate, the easier it is to carry out oxidation-reduction reactions with them.

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