Limiting reagents

Science

Definition

The limiting reagent is the reactant in a chemical reaction that is completely consumed first, determining the maximum amount of product that can be formed. The other reactant(s) left over are called excess reagents.

How It Works

  1. Write and balance the chemical equation.
  2. Convert the given amounts of each reactant to moles.
  3. Use molar ratios from the balanced equation to determine how much product each reactant could produce.
  4. The reactant that produces the least product is the limiting reagent.
  5. Calculate the theoretical yield based on the limiting reagent.

Examples

  • If you have 3 slices of bread and 5 slices of cheese, bread limits how many sandwiches you can make
  • Burning a limited amount of hydrogen gas with excess oxygen to form water
Key Fact

Theoretical yield is always calculated from the limiting reagent.

Related Terms

Stoichiometry Molar ratios Percent yield Balancing equations

Study This Concept

Practice limiting reagents with free review games in these units:

Chemistry Unit 5: Stoichiometry