What effect does a catalyst have on a chemical reaction?

A catalyst plays a crucial role in chemical reactions by lowering the activation energy, which is the minimum energy required for the reaction to proceed. By reducing this energy barrier, a catalyst allows more reactant molecules to have sufficient energy to undergo the reaction, thereby increasing the reaction rate. This means that the reaction can occur more quickly and effectively without being consumed in the process.

Catalysts operate by providing an alternative pathway for the reaction, one that requires less energy. Importantly, since catalysts are not consumed, they can be used repeatedly in multiple reactions. This characteristic is essential in both industrial applications and biological systems, where enzymes serve as biological catalysts to facilitate various biochemical reactions.

The options that suggest a catalyst increases the activation energy or decomposes reactants misrepresent the fundamental role that catalysts play in reaction dynamics. Additionally, while catalysts can influence mechanisms of reaction pathways, they do not change the direction of the reaction itself; this is determined by the thermodynamic stability of the reactants and products.