1. Stoichiometric Calculations (p. 352 – 367)
Stoichiometry – Ch. 12
Stoichiometric Calculations (p. 352 – 367)

2. 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. What is the maximum number of cookies I can make?
5 dozen
cookies
2 eggs
Ratio of eggs to cookies
5 eggs
= 12.5 dozen cookies

3. 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

4. B. Interpreting Chemical Equations
Hydrogen gas reacts with oxygen gas.
H2(g) + O2(g)  H2O(g)
What does this tell us?
2 moles H2 + 1 mole O2  2 moles H2O
Convert moles to grams!!
4.04 g H g O2  g H2O
36.04 g reactants  g products
Mole Ratios: 2 H2 : 1 O2 : 2 H2O

5. B. Interpreting Chemical Equations
Write the equation for the combustion of propane (C3H8).
C3H8(g) O2(g)  CO2(g) H2O(g)
What does this tell us?
1 mole C3H8 + 5 moles O2  3 moles CO2 + 4 moles H2O
Mole Ratios: 1 C3H8 : 5 O2 : 3 CO2 : 4 H2O

6. C. Stoichiometry Steps 1. Write a balanced equation.
2. Identify and label known & unknown.
3. Line up conversion factors.
Mole ratio – moles  moles
Molar mass – moles  grams
Molarity – moles  liters soln
Molar volume – moles  liters gas
Mole ratio – moles  moles
Core step in all stoichiometry problems!!
4. Check answer.

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

8. D. Stoichiometry Problems – Mole-Mole
NO + O2  NO2
BE SURE TO BALANCE THE EQUATION FIRST!!
If you start with 3.6 moles O2, how many moles NO2 will be produced? 2 2
3.6 mol
? mol
3.6 mol O2
2 mol NO2
1 mol O2
= 7.2 mol
NO2

9. D. Stoichiometry Problems – Mole-Mole
See handout – “Stoichiometry Practice Problems”
Work on “Part A: Mole-Mole” Problems

10. E. Stoichiometry Problems – Mole-Mole
LiBr(aq) + Cl2 (g)  LiCl(aq) + Br2(l)
How many moles of lithium chloride will be formed from mol of lithium bromide? 2 2
? mol
0.046 mol
0.046 mol LiBr
2 mol LiCl
2 mol LiBr
= mol
LiCl

11. Stoichiometry Diagram
Moles –
given
Moles –
unknown
Mole
Ratio
Molar
Mass
Molar
Mass
Grams –
given
Grams –
unknown

12. F. Stoichiometry Problems – Mole/Mass
In photosynthesis, carbon dioxide and water react to form glucose, C6H12O6 and oxygen gas.
___CO2 + ___H2O  ___C6H12O6 + ___O2
A. If 15.6 grams of carbon dioxide react, how many moles of glucose will be produced?
B. How many grams of carbon dioxide must react to produce 0.25 moles of glucose?
B – ? g
0.25 mol
A – 15.6 g
? mol 6 6 6
15.6 g CO2
1 mol CO2
1 mol C6 H12O6
= mol C6H12O6
44.01 g CO2
6 mol CO2
0.25 mol C6 H12O6
6 mol CO2
44.01 g CO2
= 66 g CO2
1 mol C6 H12O6
1 mol CO2

13. F. Stoichiometry Problems
See handout – “Stoichiometry Practice Problems”
Work on Handout – “Part B: Mole-Mass” Problems

14. G. Stoichiometry Problems – Mass/Mass
How many grams of silver will be formed from 12.0 g copper (II) reacting with silver nitrate?
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
= 40.7 g Ag

15. G. Stoichiometry Problems – Mass/Mass
Sodium metal reacts with oxygen gas to produce solid sodium oxide. How many grams of sodium must react to produce 42.0 grams of sodium oxide?
4Na + O2  2Na2O
? g
42.0 g
42.0 g Na2O
1 mol
Na2O
4 mol Na
22.99
g Na
= 31.2
g Na
61.98 g Na2O
1 mol Na
2 mol
Na2O

16. G. Stoichiometry Problems
Work on the rest of the handout:
Part C: Mass to Mole
Part D: Mass to Mass
Classwork/Homework

17. Stoichiometry WS Problem 1
How many grams of hydrogen gas would be needed to form 8.0 grams of water? 2
H2 + O2  H2O 2
? g
8.0 g
8.0 g
H2O
2 mol H2
H2O
1 mol
H2O
2.02 g H2
1 mol
= 0.90 g H2
18.02 g H2O