There are two main ways to determine the limiting reagent. One way is to find and compare the mole ratio of the amount of reactants used in the reaction (see formula 1). Another way is to calculate the grams of products produced from the given quantities of reactants; the reactant that produces the least amount of product is the limiting reagent (see formula 2).
Formula 1: Find the limiting reagent by looking at the number of moles of each reactant.
- Determine the balanced chemical equation for the chemical reaction.
- Convert all given information into moles (most likely, through the use of molar mass as a conversion factor).
- Calculate the mole ratio from the given information. Compare the calculated ratio to the actual ratio.
- Use the amount of limiting reactant to calculate the amount of product produced.
- If necessary, calculate how much is left in excess of the non-limiting reagent.
Formula 2: Find the limiting reagent by calculating and comparing the amount of product each reactant will produce.
- Balance the chemical equation for the chemical reaction.
- Convert the given information into moles.
- Use stoichiometry for each individual reactant to find the mass of product produced.
- The reactant that produces a lesser amount of product is the limiting reagent.
- The reactant that produces a higher amount of product is the excess reagent.
- To find the amount of remaining excess reactant, subtract the mass of excess reagent consumed from the total mass of excess reagent given.