Limiting Reactant

Lesson Outcome

• Understand the concept of limiting reactant.

• Recognize the limiting reactant in a reaction.

• Learn to use the limiting reactant for stoichiometric calculations.

• Identify the excess reactant.

Stoichiometric Amounts

• Definition: Stoichiometric amounts of reactants are present in a mole ratio that corresponds exactly to the mole ratio predicted by the balanced chemical equation.

• Key Point: When a reaction is complete, there are no reactants left.

Limiting and Excess Reactants

• Limiting Reactant: The reactant that is completely used up in a chemical reaction.

  • Determines how much product is produced.

  • Once exhausted, the reaction stops.

• Excess Reactant: Reactants that remain after the limiting reactant is used up.

Steps to Identify the Limiting Reactant

1. Write and balance the equation for the reaction.

2. Convert given information of reactants to moles.

3. Assume the limiting reactant using mole ratios of reactants. (Eg: Assuming CaCO₃ is the limiting reactant,……….)

4. Find the moles of product using the moles of the limiting reactant.