How can the limiting reactant in a chemical reaction be identified?

The limiting reactant in a chemical reaction is identified by calculating the amount of product formed from each reactant and determining which reactant produces the least quantity of product. This method leverages stoichiometry, where the balanced chemical equation provides the mole ratios of reactants and products.

When reactants are mixed, they do not always react in a simple 1:1 ratio, hence calculating how much product each reactant can produce based on its amount and the stoichiometric coefficients allows us to see which reactant will be completely consumed first. That reactant is the limiting reactant, as it restricts the amount of product that can be formed in the reaction.

In contrast, simply determining which reactant is used up first without calculations may lead to incorrect assumptions if one reactant appears to be consumed first due to unequal starting amounts. Measuring the mass of the reactants provides information on their initial quantities but does not directly indicate their roles in the reaction outcome without stoichiometric analysis. Using molar ratios of products can help understand the reaction but does not address the limiting nature of the reactants themselves unless paired with the amounts of reactants available.