What is the primary role of a catalyst in a chemical reaction?

A catalyst plays a vital role in chemical reactions by increasing the reaction rate. It achieves this by providing an alternative pathway for the reaction that has a lower activation energy compared to the uncatalyzed reaction. This means that more reactant molecules have the necessary energy to overcome the activation barrier, leading to an increase in the frequency of effective collisions and, consequently, a faster reaction.

This function of lowering activation energy is crucial because it allows reactions that may otherwise proceed very slowly (or not at all under certain conditions) to occur more readily. Catalysts do not permanently change or become consumed in the reaction, which means they can be used repeatedly for continuous reactions. This characteristic highlights their efficiency and utility in both laboratory and industrial settings.

The other options do not accurately describe the role of catalysts. They do not act as reactants themselves, they do not increase the activation energy, and they do not permanently alter the reactants. Understanding the role of a catalyst is fundamental in the study of kinetics and reaction mechanisms in chemistry.