What describes a substance that initiates or accelerates a chemical reaction without itself being consumed?

• A. Integrated rate law
• B. Reaction intermediate
• C. Endothermic
• D. Catalyst

Answer: (D)

A substance that initiates or accelerates a chemical reaction without itself being consumed is a catalyst. Catalysts provide an alternative, lower-energy pathway for the reaction, so more collisions have enough energy to proceed at a given temperature. Because the catalyst isn’t consumed, it remains available to catalyze additional reactions, often unchanged at the end of the process.

This fits the description because an integrated rate law is a mathematical expression describing how concentrations change over time, not a substance that speeds things up. A reaction intermediate is a species formed briefly during the reaction mechanism and then consumed, not a species that facilitates the overall rate. Endothermic describes heat flow in a reaction, not the role of a substance in changing the rate.