MCAT General Chemistry Question 69: Answer and Explanation

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Question: 69

9. Which of the following best describes the purpose of a catalyst?

  • A. Catalysts are used up in the reaction, increasing reaction efficiency.
  • B. Catalysts increase the rate of the reaction by lowering the activation energy.
  • C. Catalysts alter the thermodynamics of the reaction to facilitate the formation of products or reactants.
  • D. Catalysts stabilize the transition state by bringing it to a higher energy.

Correct Answer: B

Explanation:

By definition, a catalyst increases the rate of a reaction by lowering the activation energy, making it easier for both the forward and reverse reactions to overcome this energy barrier. Catalysts are neither used up in the reaction, nor do they alter the equilibrium of a reaction, eliminating choices (A) and (C). Finally, catalysts stabilize the transition state by lowering its energy, not raising it, eliminating choice (D).

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