Which statement best describes the effect of a catalyst?

Which statement best describes the effect of a catalyst?

• A. Increases the activation energy
• B. Has no effect on rate
• C. Only works at high temperatures
• D. Lowers the activation energy and orients collisions to facilitate reaction

Answer: (D)

A catalyst works by providing an alternative reaction pathway that has a lower activation energy and by helping reactant molecules collide in orientations that favor the reaction. By lowering the energy barrier, more collisions have enough energy to proceed to products at a given temperature, so the rate increases. The catalyst is not consumed, so it can catalyze many cycles, and it does not change the overall equilibrium constant—only the rate at which equilibrium is reached. This combination—lowering activation energy and guiding effective collisions—is why the statement describing the catalyst best captures its effect.

A catalyst works by providing an alternative reaction pathway that has a lower activation energy and by helping reactant molecules collide in orientations that favor the reaction. By lowering the energy barrier, more collisions have enough energy to proceed to products at a given temperature, so the rate increases. The catalyst is not consumed, so it can catalyze many cycles, and it does not change the overall equilibrium constant—only the rate at which equilibrium is reached. This combination—lowering activation energy and guiding effective collisions—is why the statement describing the catalyst best captures its effect.