In a chemical reaction, what is the term for the reactant that is completely consumed?

In a chemical reaction, the reactant that is completely consumed is referred to as the limiting reagent. This is the substance that determines the maximum amount of product that can be formed in a reaction. Once the limiting reagent is fully utilized, the reaction cannot proceed any further, even if other reactants are still present in excess.

The concept of the limiting reagent is fundamental in stoichiometry, which allows chemists to calculate the amounts of reactants needed and the expected yields of products based on balanced chemical equations. By identifying the limiting reagent, one can optimize reactions and minimize waste.

In contrast, the excess reagent refers to the reactants that are not completely consumed during the reaction, while a catalyst is a substance that accelerates a chemical reaction without being consumed itself. An intermediate is a species that is formed during the reaction but is not one of the final products. Understanding these distinctions helps clarify the role of each component in a chemical reaction.