1. Unit 5: Stoichiometry
Stoichiometry

2. Chemical Equations and the Mole
Remember:
a chemical equation is like a recipe – it tells you the ingredients (reactants) you need to make certain products
chemical equations tell you the relative quantities of reactants and products in a reaction

3. Chemical Equations and the Mole
How many moles do you have of each of the following?
Frame (F):
Seat (S):
Wheel (W):
Handlebar (H):
Pedal (P):
Tricycle (FSW3HP2):
1 mole
3 moles
2 moles

4. Chemical Equations and the Mole
Example:
If you had 4 moles of S and an excess of all the other reactants, how many tricycles (FSW3HP2) could you make?
We can apply the tricycle example to chemical reactions.

5. Stoichiometry
Stoichiometry: Using a known amount of one substance to predict how much of a reactant will be used or how much of a product will be produced.
You can use stoichiometry to answer questions like:
Calculate the number of grams of NH3 produced by the reaction of 5.40 g of nitrogen with an excess of hydrogen.
N2 + H2 → NH3

6. Stoichiometry – The Box Method
Calculate the number of grams of NH3 produced by the reaction of 5.40 g of nitrogen with an excess of hydrogen.
N H2 → NH3
Step 1: Balance the equation.

7. Stoichiometry – The Box Method
Calculate the number of grams of NH3 produced by the reaction of 5.40 g of nitrogen with an excess of hydrogen.
N H2 → 2NH3
grams
5.40 g *
molar mass
28.02 g/mol
g/mol
moles
Step 2: Construct the box and fill in known information (starting amount and molar masses).

8. Stoichiometry – The Box Method
Calculate the number of grams of NH3 produced by the reaction of 5.40 g of nitrogen with an excess of hydrogen.
N H2 → 2NH3
grams
5.40 g
*6.54 g
molar mass
28.02 g/mol
g/mol
moles
0.192 mol
0.384 mol
MORE x 2/1
Step 3: Calculate missing information until you determine what the problem is asking you to find.

9. Stoichiometry – The Box Method
Calculate the number of grams of NH3 produced by the reaction of 5.40 g of nitrogen with an excess of hydrogen.
N H2 → 2NH3
grams
5.40 g
*6.54 g
molar mass
28.02 g/mol
g/mol
moles
0.192 mol
0.384 mol
MORE x 2/1
Step 3: Calculate missing information until you determine what the problem is asking you to find.

10. Stoichiometry – Practice #1
How many grams of water would be produced from 60 grams of H2 and an excess of O2?
__H2 + __O2 → __H2O

11. Stoichiometry – Practice #2
How many grams of water would be produced from 60 grams of H2 and an excess of O2?
__CH4 + __O2 →