MCAT General Chemistry Question 166: Answer and Explanation
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Question: 166
1. Rusting occurs due to the oxidation–reduction reaction of iron with environmental oxygen:
4 Fe (s) + 3 O2 (g) → 2 Fe2O3 (s)
Some metals cannot react with oxygen in this fashion.
Which of the following best explains why iron can?
- A. Iron has a more positive reduction potential than those metals, making it more likely to donate electrons to oxygen.
- B. Iron has a more positive reduction potential than those metals, making it more likely to accept electrons from oxygen.
- C. Iron has a less positive reduction potential than those metals, making it more likely to donate electrons to oxygen.
- D. Iron has a less positive reduction potential than those metals, making it more likely to accept electrons from oxygen.
Correct Answer: C
Explanation:
In the oxidation-reduction reaction of a metal with oxygen, the metal will be oxidized (donate electrons) and oxygen will be reduced (accept electrons). This fact allows us to immediately eliminate choices (B) and (D). A species with a higher reduction potential is more likely to be reduced, and a species with a lower reduction potential is more likely to be oxidized. Based on the information in the question, iron is oxidized more readily than those metals; this means that iron has a lower reduction potential.