1. Chapter 7- Quantities in Chemical reactions
(7.1) Stoichiometry-Part 1

2. Stoichiometry
The information we can get from balanced chemical equations help us with our calculations of chemical reactions.

3. Stoichiometry of S’mores
Imagine you are making the Perfect S’more
You will need:
2 Graham Crackers
4 Chocolate Squares
1 Marshmallow

4. 2 S’mores
How many of each ingredient would you need to make 2 S’mores?
4 Graham Crackers
8 Chocolate Squares
2 Marshmallows

5. Stoichiometric Relationships
The numerical relationship between the quantities of reacting substances that corresponds to the laws of stoichiometry.
Stoichiometric relationships are expressed in whole numbers.

6. Types of Stoichiometric Relationships
Particle : Particle
Mole : Mole
Mass : Mass

7. Particle : Particle Relationship
The coefficient in a balanced chemical equation tells us how many atoms or molecules are involved.
N2(g) H2(g)  NH3(g)
1 molecule 3 molecules 2 molecules
Ex 1) If you want to produce 12 molecules of ammonia, how many molecules of nitrogen do you need?

8. Particle : Particle Relationship
N2(g) + 3 H2(g)  2 NH3(g) 1 molecule 3 molecules 2 molecules Ex 2) If 30 molecules of hydrogen react, how many molecules of ammonia will be formed?

9. Mole : Mole Relationship
The coefficients in a chemical equation can also represent moles.
N2(g) H2(g)  2 NH3(g)
1 mole moles moles
Ex 3) If 3.2 moles of hydrogen react, how many moles of ammonia will be produced?

10. C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(g)
Example 4
The balanced chemical equation for the combustion of propane is:
C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(g)
a) How many mole of O2 are needed to react with mol of C3H8?
b) If 3.00 mol of C3H8 burn completely in O2, how many moles of CO2 are produced?
c) How many molecules of O2 are needed to react with 2.00 mol of C3H8?
Work out on board (remind students to write this down)

11. Example 4 – Answers a) n = 2.50 mol O2 b) n = 9.00 mol CO2
c) N = 6.02x1024 molecules O2

12. Homework Read 234-240 Textbook: p237 # 1-2 p238 # 4 – 7
(check answers on p273)
P240 # 8-10