Which concept describes a substance that lowers the activation energy without being consumed in the reaction?

• A. Arrhenius
• B. Catalyst
• C. Rate Law
• D. Reaction coordinate diagram

Answer: (B)

Activation energy is the energy barrier that must be overcome for a reaction to proceed. A catalyst provides an alternative reaction pathway with a lower energy barrier, so the reaction runs faster. The key is that the catalyst is not consumed in the overall process; it interacts to speed things up and is regenerated, ready to catalyze more cycles. Because of this regeneration, even a small amount of catalyst can accelerate large amounts of reactants. This idea fits the concept of a substance that lowers the activation energy without being consumed. In contrast, the Arrhenius framework describes how rate constants depend on temperature and activation energy but doesn’t specify a substance that remains unchanged; the Rate Law states how rate depends on concentrations; and a reaction coordinate diagram shows energy changes along the pathway, which can illustrate a lower barrier for a catalyzed route but is a diagram, not the substance itself.