Which concept describes something that increases the rate of a reaction without being consumed?

• A. Catalyst
• B. Inhibitor
• C. Acid
• D. Base

Answer: (A)

A catalyst is a substance that increases the rate of a reaction without being consumed. It works by providing an alternative reaction path that has lower activation energy, so more reacting molecules have enough energy to reach the transition state and form products each second. Because the catalyst is not used up in the process, it remains present after the reaction and can speed up additional reactions. Enzymes are a familiar example of catalysts in biology. The other options don’t describe this effect: inhibitors slow or stop reactions by interfering with steps in the mechanism, and acids or bases are defined by their ability to donate or accept protons (pH-related properties), not by increasing reaction rate without being consumed.