Which statement best describes how a catalyst affects the reaction rate?

Which statement best describes how a catalyst affects the reaction rate?

• A. It speeds up the rate by decreasing activation energy.
• B. It speeds up the rate by increasing temperature.
• C. It changes the stoichiometric coefficients.
• D. It shifts the equilibrium constant.

Answer: (A)

Catalysts affect reaction rate by providing an alternate pathway with lower activation energy. By offering a lower energy barrier, more molecules have enough energy to reach the transition state at a given temperature, so collisions that lead to product formation occur more often and the reaction speeds up. A catalyst is not consumed in the reaction, and it does not change the overall amount of reactants or products (the stoichiometric coefficients stay the same). It also doesn’t alter the equilibrium constant or shift the position of equilibrium at a fixed temperature, although it does speed up how quickly that equilibrium is reached. While increasing temperature can raise the rate by supplying more energy, that effect comes from temperature, not from the catalytic pathway itself.

Catalysts affect reaction rate by providing an alternate pathway with lower activation energy. By offering a lower energy barrier, more molecules have enough energy to reach the transition state at a given temperature, so collisions that lead to product formation occur more often and the reaction speeds up. A catalyst is not consumed in the reaction, and it does not change the overall amount of reactants or products (the stoichiometric coefficients stay the same). It also doesn’t alter the equilibrium constant or shift the position of equilibrium at a fixed temperature, although it does speed up how quickly that equilibrium is reached. While increasing temperature can raise the rate by supplying more energy, that effect comes from temperature, not from the catalytic pathway itself.