1. 1 Chapter 9-Stoichiometry Stoichiometry – measures and calculates amounts of chemicals in a reaction. A.Mole/Mole Problems Coefficients: Show # of molecules in equations Show # of moles in equations

2. 2 Example: Glucose reacts with oxygen to produce carbon dioxide and water vapor in cellular respiration. a. Write a balanced equation for this reaction. b.If 0.30 moles of glucose are reacted, how many moles of carbon dioxide will be produced?

3. 3 c. If 0.15 moles of glucose are reacted, how many moles of oxygen are reacted? d. If 0.26 moles of water are produced, how many moles of glucose are reacted?

4. 4 B. Mass Stoichiometry Problems **First-Write a Balanced Equation** 1. Change to Moles 2. Use Coefficients (=Mole Ratios) changes chemical 3. Change to what is asked for May not need steps 1 or 3 – depends on what you are given and what is asked for.

5. 5 Examples: 1. Hydrogen peroxide (H 2 O 2 ) decomposes to form water and oxygen gas. If 25.0 grams of hydrogen peroxide decompose, how many grams of oxygen will be produced?

6. 6 2. 55.0 grams of hydrogen fluoride are completely reacted with tin. How many moles of tin (II) fluoride are produced?

7. 7 C. Limiting & Excess Reactants Reactants are not always completely used up in a reaction. Excess Reactant = reactant that has leftovers at the end of the reaction. Limiting Reactant = reactant that is completely used up in the reaction **makes the least product**

8. 8 Example: 2.25 grams of PCl 3 are mixed with 1.23 grams of H 2 O in the following reaction: PCl 3 + 3H 2 O  H 3 PO 3 + 3HCl a.Calculate the limiting & excess reactants

9. 9 b. How many grams of HCl will be produced? c. How many grams of the excess reactant will be left?

10. 10 D. Percent Yield Grams of Product calculated from limiting reactant = Theoretical Yield *This is amount of product that should be produced if experiment is 100% perfect. Amount really produced = Actual Yield %Yield = Actual Yield x 100 Theoretical Yield

11. 11 Example: When 14.0 grams of nitrogen gas are mixed with 9.0 grams of hydrogen gas, 16.1 grams of ammonia gas are formed. 1. Write a balanced equation for this reaction.

12. 12 2. Calculate to find the limiting & excess reactants. 3. What is the theoretical yield in grams of ammonia?

13. 13 4. What is the percent yield of ammonia in this reaction? 5. How many grams of the excess reactant are left?