1. Limiting and Excess Reactants

2. LIMITING REACTANTS
LIMIT HOW MUCH OF THE PRODUCT CAN ACTUALLY BE PRODUCED DURING THE REACTION

3. EXCESS REACTANTS
The reactants that are left over when the reaction stops.
*When all the limiting reactant is used up

4. How to find the limiting reactants
Solve each of the problems
Which of the problems produces the least amount?
This is your Limiting Reactant

5. Finding the limiting reactants
NaOH + HCl ⇒ H2O + NaCl If there are 25 grams of NaOH, how many grams of H2O will be formed? If there are 16 grams of HCl, how many grams of H2O will be formed? Which is the limiting reactant?______________________

6. Finding the limiting reactant
2H2 + O2 ⇒ 2H2O Determine the limiting reactant and how much water will be formed from it, if the following is true: 3 grams of H2 and 5 grams of O2

7. Percent Yield

8. Percent Yield Actual Yield x 100 = Percent Yield Theoretical Yield
This is a measurement of the accuracy of the chemical reaction.
Actual Yield: is the amount of product actually produced, and measured at the end of the reaction.
Theoretical Yield: (expected value) is how much product was expected to be produced. This is done by calculating how much should be produced based on the amounts of beginning products.
Actual Yield
Theoretical Yield
x 100 = Percent Yield

9. How to determine the % yield:
Complete the conversions of both givens
Determine which substance is the limiting reactant
Use the limiting reactant as the theoretical yield
Calculate the percent yield
Divide the actual yield by the theoretical yield
Multiply by 100
*This determines how accurate your reaction was in percentage

10. Determining the % Yield:
Mg(OH)2 + 2NaCl ⇒ 2NaOH + MgCl2
Determine the limiting reactant and how many grams of MgCl2 will be formed from it, if there are 4.6 grams of Mg(OH)2 and 7.8 grams of NaCl.
What is the % yield if only 5.78g of MgCl2 was collected at the end of the experiment/reaction?

11. Determining the % Yield:
2H2 + O2 ⇒ 2H2O
Determine the limiting reactant and how much water should be formed from it, if 3 grams of H2 and 5 grams of O2.
3g H2 1 mol H2 2 mols H2O 18g H2O
= 27g H2O
2g H2 2 mols H mol H2O
5g O2 1 mol O2 2 mols H2O g H2O
= 5.625g H2O
32g O2 1 mol O mol H2O
What is the percent yield, if the chemist only gathers 3.78g of H2O at the end of the reaction?