What role do limiting reactants play in a chemical reaction's yield?

In a chemical reaction, the limiting reactant is the substance that is entirely consumed first, thereby stopping the reaction and determining how much product can be formed. This is crucial because the yield of a reaction—the actual amount of product produced—depends directly on the quantity of the limiting reactant available. Once this reactant is used up, the reaction cannot proceed further, even if other reactants are present in excess.

For instance, in a reaction involving a limiting reactant, if you have five molecules of substance A, and it reacts with substance B, but only three molecules of B are available, then A is the limiting reactant. This means that only a certain maximum amount of product can be produced based on the amount of A, regardless of how much B is available. Thus, understanding the role of the limiting reactant is essential for predicting the yield of the reaction accurately.