How do you find the limiting reactant in a chemical reaction using moles?

To find the limiting reactant in a chemical reaction using moles, compare the mole ratios of the reactants to their coefficients in the balanced equation.

In a chemical reaction, the limiting reactant is the substance that is completely consumed when the reaction is complete. It determines the maximum amount of product that can be formed. To identify the limiting reactant using moles, you first need to balance the chemical equation. This gives you the stoichiometric ratios, or the ratios in which the reactants combine to form the products.

Next, convert the given amounts of the reactants into moles. This is 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, compare these to the stoichiometric ratios from the balanced equation. Divide the number of moles of each reactant by the coefficient in front of it in the balanced equation. The reactant that gives the smallest result is the limiting reactant. This is because it will be used up first in the reaction.

For example, consider the reaction 2H2 + O2 → 2H2O. If you have 4 moles of H2 and 1 mole of O2, you would divide 4 by 2 (the coefficient in front of H2) to get 2, and 1 by 1 (the coefficient in front of O2) to get 1. Since 1 is smaller than 2, O2 is the limiting reactant.

Remember, the limiting reactant is not necessarily the reactant that is present in the smallest amount. It is the reactant that is present in the smallest amount relative to how much is needed for the reaction.