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.

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