How does one determine the limiting reactant in a reaction?

The limiting reactant in a reaction is determined by calculating the amount of product each reactant can produce.

In a chemical reaction, the limiting reactant (or limiting reagent) is the substance that is completely consumed when the reaction is complete. It determines the maximum amount of product that can be formed from the reactants. To identify the limiting reactant, you need to know the balanced chemical equation for the reaction and the amount of each reactant present at the start.

Firstly, write down the balanced chemical equation for the reaction. This will tell you the stoichiometric ratios, or the ratios in which the reactants combine to form the products. For example, in the reaction 2H2 + O2 → 2H2O, two molecules of hydrogen react with one molecule of oxygen to form two molecules of water.

Next, calculate the number of moles of each reactant. This can be done by dividing the mass of each reactant by its molar mass. The molar mass is the mass of one mole of a substance, and can be found by adding up the atomic masses of all the atoms in a molecule of the substance.

Once you have the number of moles of each reactant, you can calculate the amount of product that each reactant could produce if it were completely consumed. This is done by multiplying the number of moles of the reactant by the stoichiometric ratio from the balanced chemical equation.

The reactant that produces the least amount of product is the limiting reactant. This is because it will be completely consumed before the other reactants, stopping the reaction. The amount of product that this reactant can produce is the theoretical yield of the reaction.

Remember, the limiting reactant is not necessarily the reactant that is present in the smallest quantity. It is the reactant that produces the least amount of product. This is an important concept in chemistry, as it allows us to predict the outcome of a reaction and to plan reactions so that they are as efficient as possible.