Which of the following statements about catalysts is true?

• A. A catalyst increases the equilibrium constant of a reaction.
• B. A catalyst is consumed during the reaction.
• C. A catalyst changes the overall enthalpy change (ΔH) of a reaction.
• D. A catalyst lowers the activation energy of a reaction.

Answer: (D)

Verified step by step guidance

1. Understand what a catalyst does in a chemical reaction: it provides an alternative reaction pathway with a lower activation energy, which speeds up the reaction.
2. Recall that a catalyst is not consumed in the reaction; it participates in the reaction mechanism but is regenerated by the end.
3. Know that a catalyst does not change the equilibrium constant (K) of a reaction because it affects the rate at which equilibrium is reached, not the position of equilibrium itself.
4. Recognize that the overall enthalpy change (\$\Delta H\$) of a reaction is a state function and depends only on the initial and final states, so a catalyst does not alter \$\Delta H\$.
5. Conclude that the true statement is: a catalyst lowers the activation energy of a reaction, thereby increasing the reaction rate without changing the equilibrium or thermodynamics.