Question: Which of the following statements about reaction mechanisms is true?

Options:

1. All reactions proceed through a single elementary step.
2. Catalysts are consumed in the reaction.
3. The rate-determining step is the slowest step in a mechanism.
4. Intermediates are always stable.

Correct Answer: The rate-determining step is the slowest step in a mechanism.

Solution:

The rate-determining step is indeed the slowest step in a reaction mechanism, which controls the overall rate of the reaction.