Which statement about catalysts and chemical equilibria is true?

• A. A catalyst shifts the equilibrium position.
• B. A catalyst changes the equilibrium constant.
• C. A catalyst speeds up attainment of equilibrium but does not alter the position.
• D. A catalyst changes the temperature at which equilibrium occurs.

Answer: (C)

Catalysts influence how fast a system reaches equilibrium, not where the balance lies. They provide an alternate reaction pathway with a lower activation energy, which increases the rate constants for both the forward and reverse reactions. Because both directions are sped up by the same factor, the equilibrium constant—the ratio of product to reactant concentrations at equilibrium—stays the same at a given temperature. The position of equilibrium is governed by thermodynamics, not by the presence of a catalyst, so it does not shift. Temperature, too, sets the equilibrium constant, and a catalyst does not change the temperature at which equilibrium occurs; it only speeds up how quickly equilibrium is reached. So the correct statement is that a catalyst speeds up attainment of equilibrium but does not alter the position.