Excess reactant — Science definition
A reactant that is left over after the limiting reactant is completely used up.
Where it is taught
- Limiting Reactants & Percent Yield — Stoichiometry & Yield, Physical Science: Chemistry, Grade 11
In use
Whatever is left over when it is gone is the excess reactant.
Limiting Reactants & Percent Yield
Questions using excess reactant
Problem 1
Explain why adding even more of the excess reactant does not increase the amount of product formed.
Answer and explanation
Once the limiting reactant is completely used up, the reaction stops — there is nothing left for the extra excess reactant to react with. The product amount is capped by the limiting reactant, so adding more excess just leaves more of it unreacted.