When a catalyst is added to a reversible chemical reaction, what effect does it have on the rates of the forward and reverse reactions?

• A. Neither reaction rate is affected.
• B. Only the reverse reaction rate increases.
• C. Both the forward and reverse reaction rates increase.
• D. Only the forward reaction rate increases.

Answer: (C)

Verified step by step guidance

1. Understand that a catalyst provides an alternative reaction pathway with a lower activation energy, which affects how quickly the reaction reaches equilibrium.
2. Recall that in a reversible reaction, there are two simultaneous processes: the forward reaction and the reverse reaction, each with its own rate.
3. Recognize that a catalyst lowers the activation energy barrier for both the forward and reverse reactions equally, because it stabilizes the transition state for both directions.
4. Conclude that since the activation energy is lowered for both directions, the rates of both the forward and reverse reactions increase when a catalyst is added.
5. Note that although the rates increase, the catalyst does not change the position of equilibrium; it only helps the system reach equilibrium faster.