Which statement best describes how a catalyst affects a chemical reaction?

• A. It is consumed during the reaction and becomes part of the products.
• B. It changes the enthalpy change (ΔH) of the reaction.
• C. It increases the rate of the reaction by lowering the activation energy.
• D. It increases the equilibrium constant of the reaction.

Answer: (C)

Verified step by step guidance

1. Understand the role of a catalyst in a chemical reaction: a catalyst provides an alternative reaction pathway with a lower activation energy, which increases the reaction rate.
2. Recall that a catalyst is not consumed in the reaction; it participates temporarily and is regenerated by the end of the reaction.
3. Recognize that a catalyst does not change the overall enthalpy change (\$\Delta H\$) of the reaction because it does not alter the initial or final energy states of the reactants and products.
4. Know that a catalyst does not affect the equilibrium constant of the reaction since it speeds up both the forward and reverse reactions equally, allowing equilibrium to be reached faster but not changing its position.
5. Conclude that the best description of a catalyst's effect is that it increases the rate of the reaction by lowering the activation energy.