1. Limiting Reactants & Percent Yield

3. Definitions  Limiting Reactant - completely consumed in the reaction and determines the amount of product formed  Excess Reactant - some amount remains left over at the end of reaction

4. Limiting Reactant Problems  2 starting amounts of reactants are given  The reactant that makes the least theoretical amount of product = Limiting  The reactant that makes more theoretical product = Excess  This much can’t be made  Some reactant is not used and still remains

5. Limiting Reactant Worksheet Consider the following reaction: 2 Al + 6 HBr → 2 AlBr 3 + 3 H 2  a. When 3.22 moles of Al reacts with 4.96 moles of HBr, how many moles of H 2 are formed?  b. What is the limiting reactant?  c. For the reactant in excess, how many moles are left over at the end of the reaction?

6. Percent Yield  The maximum amount of product that can be obtained from a reaction is the theoretical yield  Frequently, the actual yield (the amount obtained in the lab) is less.  Percent Yield = actual X 100% theoretical