MCAT General Chemistry Question 281: Answer and Explanation
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Question: 281
7. Which of the following best describes how a catalyst might speed up a reaction?
- A. It raises the temperature of the reaction mixture.
- B. It raises the activation energy, making it easier to overcome the energy barrier.
- C. It increases the rate of the slowest step.
- D. It increases the frequency of collisions between molecules.
Correct Answer: C
Explanation:
C Catalysts don't work by raising the temperature of the reaction mixture, so choice A is eliminated. They lower the activation energy, not raise it, so choice B is wrong. Catalysts sometimes work by speeding up the slowest step (and sometimes by providing an alternate, faster reaction mechanism), so choice C is a viable answer. Catalysts can't change the frequency of collisions between molecules, leaving choice C as the best answer.