1. Mole Review
1.) Calculate the number of moles in 60.4L of O2. 2.) How many moles are there in 63.2g of Cl2?
1 mol O2
60.4L O2
= 2.7 mol O2
22.4L O2
1mol Cl2
63.2g Cl2
= 0.903mol Cl2
70g Cl2

2. Math In Chemistry Stoichiometry
Unit 08
Math In Chemistry
Stoichiometry

3. Scheduled to make 640 tricycles. How many wheels should they order?
Proportional Relationships
Tiny Tyke Tricycle Company
F + S + 3W + H + 2P → FSW3HP2
Scheduled to make 640 tricycles. How many wheels should they order?

4. 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. Proportional Relationships
Stoichiometry
mass relationships between substances in a chemical reaction
for example: you can determine the amount of a compound required to make another compound
based on the mole ratio
Mole Ratio
indicated by coefficients in a balanced equation
2 Mg + O2  2 MgO
2 Moles of magnesium react with 1 mole of oxygen to form 2 moles of magnesium oxide.

6. 2 Mg + O2  2 MgO
What would be the mole ratio of magnesium to magnesium oxide? 2 : 2 Conversion factor = 2 mol Mg 2 mol MgO What would be the mole ratio of oxygen to magnesium? 1 : 2 Conversion factor = 1 mol O2 (Mole Ratio) 2 mol Mg

7. Practice
5 F2 + 2NH3  N2F4 + 6HF
1. What is the mole ratio of NH3 to F2?
Write the mole ratio as a conversion factor.
2. What is the mole ratio of HF to N2F4?
2:5
2mol NH3
5mol F2
6:1
6mol HF
1mol N2F4

8. Stoichiometry Steps 1. Identify known & unknown.
2. Convert known to mole. (if necessary)
3. Use Mole Ratio.
4. Convert moles to unknown unit. (if necessary)
Mole ratio- get from equation
Units of unknown
known
Mol of unknown
Mol of known
Mol of unknown

9. Mass-Mass Stoichiometry
Mass of reactants equals the products
Law of Conservation of Mass
ONLY mass and atoms are conserved in every chemical reaction
Known g
1 mol Known
Molar mass
Known
mol unknown
mol known
Mol ratio-
get from equation
Molar mass unknown
1 mol unknown

10. Mass-Mass Stoichiometry#1
The reaction of fluorine with ammonia produces dinitrogen tetrafluoride and hydrogen fluoride.
5F2 + 2 NH3 → N2F4 + 6HF
How many grams of NH3 are required to produce 7.38g HF?

11. Mass-Mass Stoichiometry#2
5F2 + 2 NH3 → N2F4 + 6HF
How many grams of N2F4 can be produced from 265g F2?

12. Mass-Mass Stoichiometry#3
2C2H2 + 5O2 → 4CO2 + 2H2O
How many grams of oxygen are required to burn 52.0g C2H2?

13. C. 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
= 40.7 g Ag

14. C. Stoichiometry Problems
Calculate the number of grams of NH3 produced by the reaction of 5.40 g of hydrogen with an excess of nitrogen.
N2 + 3H2 → 2NH3

15. C. Stoichiometry Problems
Acetylen gas (C2H2) is produced by adding water to calcium carbide (CaC2).
CaC2 + 2H2O  C2H2 + Ca(OH)2
How many grams of acetylene are produced by adding water to 5.00 g CaC2?
Using the same equation, determine how many moles of CaC2 are needed to react completely with 49.0 g H2O.

16. Mole-Mole Examples __S + __O2 → __SO3 Write the equation.#1
__S + __O2 → __SO3
Write the equation.
Balance the equation.
How many moles of SO3 are produced when there are 4.5 moles of S?
Known =
Unknown =

17. Mole-Mole Examples 2C3H7OH + 9O2 → 6CO2 + 8H2O Write the equation.#2
Isopropyl alcohol (C3H7OH) burns in the air to this equation:
2C3H7OH + 9O2 → 6CO2 + 8H2O
Write the equation.
Calculate the moles of oxygen needed to react with 3.40 moles of isopropyl alcohol.

18. Mole-Mole Examples 2C3H7OH + 9O2 → 6CO2 + 8H2O#3
2C3H7OH + 9O2 → 6CO2 + 8H2O
Find the moles of water when 6.20 mol O2 reacts with C3H7OH.

19. C. 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

20. Volume-Volume Stoichiometry
Formula to use:
Known (L) 1 mol known mol unknown L unknown
L known mol known mol unknown

21. Volume Example C3H8 + 5O2 → 3CO2 + 4H2O#4
C3H8 + 5O2 → 3CO2 + 4H2O
If 20 liters of oxygen are consumed in the above reaction, how many liters of carbon dioxide are produced?

22. C. Mixed 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

23. C. Mixed Stoichiometry Problems
How many grams of KClO3 are required to produce 9.00 L of O2 at STP?
2KClO3  2KCl + 3O2
? g
9.00 L
9.00 L O2
1 mol O2
22.4 L
2 mol
KClO3
3 mol O2
122.55
g KClO3
1 mol
KClO3
= 32.8 g
KClO3

24. Limiting Reactants/Reagents
Available Ingredients
4 slices of bread
1 jar of peanut butter
1/2 jar of jelly
Limiting Reactant/Reagents
bread
Excess Reactants/Reagents
peanut butter and jelly

25. Limiting Reactants/Reagents
Limiting Reactant/Reagent
used up in a reaction
determines the amount of product
Excess Reactant/Reagent
added to ensure that the other reactant is completely used up
cheaper & easier to recycle

26. Limiting Reagents 1. Write a balanced equation.
2. For each reactant, calculate the amount of product formed.
3. Smaller answer indicates:
limiting reactant
amount of product

27. Limiting Reagents Zn + 2HCl  ZnCl2 + H2
79.1 g of zinc react with 0.90 L of HCl. Identify the limiting and excess reactants. How many liters of hydrogen are formed at STP?
Zn HCl  ZnCl H2
79.1 g
0.90 L
? L

28. Limiting Reagents Zn + 2HCl  ZnCl2 + H2 79.1 g 0.90 L ? L 79.1 g Zn
1 mol Zn 65
g Zn
1 mol H2 Zn
22.4 L H2
1 mol
= 27.3 L H2

29. Limiting Reagents Zn + 2HCl  ZnCl2 + H2 79.1 g 0.90 L ? L 0.90 L HCl
1 mol
HCl
22.4
L HCl
1 mol H2
2 mol
HCL
22.4 L H2
1 mol
= 0.45 L H2

30. Limiting Reagents Zn: 27.3 L H2 HCl: 0.45 L H2 Limiting reagent: HCl
Excess reagent: Zn

31. Percent Yield
Percent yield- the ratio of the actual yield to the theoretical yield
Actual yield- the amount of product formed when a reaction is carried out in the laboratory
Theoretical yield- the calculated amount of product formed during a reaction

32. Percent Yield
measured in lab
calculated on paper 32

33. Percent Yield K2CO3 + 2HCl  2KCl + H2O + CO2
When 45.8 g of K2CO3 react with excess HCl, 46.3 g of KCl are formed. Calculate the theoretical and % yields of KCl.
K2CO3 + 2HCl  2KCl + H2O + CO2
45.8 g
? g
actual: 46.3 g

34. Formulas to Use Mole - Mole Known mol of unknown mol of known
Mol Ratio – from equation
Mass - Mass
mol of unknown
Known g
1 mol known
molar mass unknown
mol of known
1 mol unknown
molar mass known OR OR
Other
6.02 × 1023 particles
mol of unknown
Known L
1 mol known
22.4 L unknown OR
particles
mol of known
1 mol unknown
22.4 L known
6.02 × 1023 particles

35. 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

36. Stoichiometry Problems
How many grams of KClO3 are req’d to produce 9.00 L of O2 at STP?
2KClO3  2KCl + 3O2
? g
9.00 L
9.00 L O2
1 mol O2
22.4 L
2 mol
KClO3
3 mol O2
122.55
g KClO3
1 mol
KClO3
= 32.8 g
KClO3

37. 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
= 40.7 g Ag

38. Stoichiometry Problems
How many grams of Cu are required to react with 1.5 L of 0.10M AgNO3?
Cu + 2AgNO3  2Ag + Cu(NO3)2
? g
1.5L
0.10M
1.5 L
.10 mol
AgNO3
1 L
1 mol Cu
2 mol
AgNO3
63.55
g Cu
1 mol Cu
= 4.8 g Cu