MCAT General Chemistry Question 241: Answer and Explanation

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Question: 241

3. Which of the following best characterizes the spontaneous half-reaction below under standard conditions?

Pd2+ + 2e- → Pd

  • A. ∆G° > 0 and E° < 0
  • B. ∆G° < 0 and E° < 0
  • C. ∆G° > 0 and E° > 0
  • D. ∆G° < 0 and E° > 0

Correct Answer: D

Explanation:

D This question is asking about two factors (a two by two question): ∆G° and E°, which are related by ∆G° = -nFE°. For any spontaneous reaction, the change in Gibbs free energy (∆G°) is always less than 0 (eliminate choices A and C). As shown in the equation above, the standard reduction potential (E°) must be positive when ∆G° is negative, so eliminate choice B.

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