1. Mathematics in Chemistry
Stoichiometry
Mathematics in Chemistry

2. Review: Calculations: 1 mole = 6.02 x 1023 molecules, form.units
1 mole = x grams, x is molar mass

3. Review: Molar Mass C10 H6 O3 TOTAL = 174.1 grams
10 C = 10 X 12.01g =
6 H = 6 X g =
3 O = 3 X 16.00g =
TOTAL = grams

4. Review: Chemical Equations:
Recipe for a Chemical Reaction
Relative number of Reactant and Product
CH4 + O2  CO2 + H2O

5. Review: Balancing Continued:
C2H5OH (l) + 3O2 (g)  2CO2 (g) + 3H2O (g)

6. Basics of Stoichiometry
Al + O2 → Al2O3
If the equation is not balanced, the first step is to balance the equation.
4 Al + 3 O2 → 2 Al2O3

7. Mole  Mole 4Al + 3O2 → 2Al2O3
How many moles of aluminum are in 6.40 moles of Aluminum Oxide? Step 1: Determine the ratio needed 4 mol Al or 2 mol Al2O3 2 mol Al2O3 4 mol Step 2: Set up the problem using dimensional analysis mol Al2O3 =
4 mol Al
mol Al
2 mol Al2O3
This is the Ratio determined in step 1

8. Mole  Mass 4Al + 3O2 → 2Al2O3
How many grams of aluminum are in 8.00 moles of oxygen? Step 1: Determine the ratio needed: 4 mol Al or 3 mol O2 3 mol O2 4 mol Al 8.00 mol O2 = g Al Steps: given – ratio – molar mass
Step 2: Set up the problem
4 mole Al
26.98 g Al
287.79
3 mole O2
1 mole Al
This is the Ratio determined in step 1

9. Mass  Mole 4Al + 3O2 → 2Al2O3
How many moles of oxygen are in g of aluminum oxide? Step 1: Determine the ratio needed. 2 mol Al2O3 or 3 mol O2 3 mol O2 2 mol Al2O3 Step 2: Set up the problem g Al2O3 = mol O2 Steps: given – molar mass - ratio
This is the Ratio determined in step 1
1 mol Al2O3
3 mol O2
2.27
g Al2O3
2 mol Al2O3

10. Mass  Mass 4Al + 3O2 → 2Al2O3
How many grams of oxygen are in 54 g of aluminum? Step 1: Determine the ratio needed. 4 mol Al or 3 mol O2 3 mol O2 4 mol Al Step 2: Set up the problem Steps: Given – Molar Mass – Ratio – Molar Mass
This is the Ratio determined in step 1
32 g O2 =
48.04 g O2
1 mol Al
3 mol O2
54 g Al
1 mol O2
26.98 g Al
4 mol Al