1. Stoichiometric Calculations
Stoichiometry
Stoichiometric Calculations

2. Chocolate Chip Cookies!!
1 cup butter
1/2 cup white sugar
1 cup packed brown sugar
1 teaspoon vanilla extract
2 eggs
2 1/2 cups all-purpose flour
1 teaspoon baking soda
1 teaspoon salt
2 cups semisweet chocolate chips
Makes 3 dozen
How many eggs are needed to make 3 dozen cookies?
How much butter is needed for the amount of chocolate chips used?
How many eggs would we need to make 9 dozen cookies?
How much brown sugar would I need if I had 1 ½ cups white sugar?

3. Cookies and Chemistry…Huh!?!?
Just like chocolate chip cookies have recipes, chemists have recipes as well
Instead of calling them recipes, we call them reaction equations
Furthermore, instead of using cups and teaspoons, we use moles
Lastly, instead of eggs, butter, sugar, etc. we use chemical compounds as ingredients

4. A. Proportional Relationships
2 1/4 c. flour
1 tsp. baking soda
1 tsp. salt
1 c. butter
3/4 c. sugar
3/4 c. brown sugar
1 tsp vanilla extract
2 eggs
2 c. chocolate chips
Makes 5 dozen cookies.
I have 5 eggs. How many cookies can I make?
Ratio of eggs to cookies
5 eggs
5 doz.
2 eggs
= 12.5 dozen cookies

5. A. Proportional Relationships
Stoichiometry
mass relationships between substances in a chemical reaction
based on the mole ratio
Mole Ratio
indicated by coefficients in a balanced equation
2 Mg + O2  2 MgO

6. B. Stoichiometry Steps 1. Write a balanced equation.
2. Identify known & unknown.
3. Line up conversion factors.
Mole ratio - moles  moles
Molar mass - moles  grams
Mole ratio - moles  moles
Core step in all stoichiometry problems!!
4. Check answer.

7. 2H2 + O2  2H2O Means 2 moles H2 + 1 mole O2  2 Moles H2O
Amount of moles
2H2 + O2  2H2O Means 2 moles H2 + 1 mole O2  2 Moles H2O

8. Amount of Atoms 2H2 + O2  2H2O Means 4 atoms H + 2 atoms O 
4 atoms H and 2 atoms O

9. Amount of Molecules 2H2 + O2  2H2O Means
2 molecule H2 + 1 molecule O2  2 Molecules H2O

10. Mass
2H2 + O2  2H2O
Means
(2x2.02) g H g O2  (2x18.02) g H2O

11. Ratios
2H2 + O2  2H2O 2 moles H2 2 moles H2 1 mole O2 2 moles H2O 1 mole O2 * FLIP FLOP THESE 2 moles H2O

12. D. Stoichiometry Problems
How many moles of KClO3 must decompose in order to produce 9 moles of oxygen gas?
2KClO3  2KCl + 3O2
? mol
9 mol
9 mol O2
2 mol KClO3
3 mol O2
= 6 mol
KClO3

13. D. Stoichiometry Problems
How many grams of silver will be formed from 12.0 g copper?
Cu + 2AgNO3  2Ag + Cu(NO3)2
12.0 g
? g
12.0
g Cu
1 mol Cu
63.55
g Cu
2 mol Ag
1 mol Cu
107.87
g Ag
1 mol Ag
= g Ag