Which statement about a catalyst is true?

• A. It is consumed in the reaction
• B. It lowers the activation energy but is consumed
• C. It lowers the activation energy without being consumed
• D. It changes the overall enthalpy of the reaction

Answer: (C)

A catalyst works by providing an alternative reaction pathway that has a lower energy barrier to reach the transition state. This lowers the activation energy, so more reactant molecules have enough energy to react at a given temperature, which speeds up the reaction. Importantly, the catalyst itself is not consumed in the process; it participates in the mechanism but is regenerated at the end of the cycle, ready to catalyze again. Because the energy difference between reactants and products (the overall enthalpy change, ΔH) is determined by the thermodynamics of the reactants and products, a catalyst does not alter ΔH. So the best description is that a catalyst lowers the activation energy without being consumed, and it does not change the overall enthalpy of the reaction.