1. Chapter 3: Mass Relations:
Stoichiometry: The study of mass relations in chemistry

2. Stoichiometry
All Stoichiometry is based on the Law of Conservation of Mass

3. Section 11-1

4. 3.1 Atomic Masses
Atomic mass unit (AMU) is defined as 1/12th the mass of a carbon – 12 atom.
The weighted average of the masses of the isotopes of an element create the elements atomic mass.
Remember completing weighted avg???

5. Atomic Mass vs. Molar Mass
A.M.U works for theory, but we can not measure individual atoms
Must create molar mass.
Avagadro’s number, number of atoms of carbon-12 it takes to weigh exactly 12 grams.
6.02 x 1023 atoms = 1 mole

6. 3.2 Mole Mountain #1

7. 3.3 Percent Composition Remember the poison worksheet?
What is the % of Carbon in glucose C6H12O6

8. 3.4 Reaction Stoichiometry
How do we know how much we need, how much will be created.
Think of a reaction as a recipe,
Reactants → Products
Must be a Balanced Equation

9. Mole Mt. # 2

10. Limiting Reactant Why do reactions stop?
Eventually we run out of reactants
The reactant we run out of first, stopping the reaction, is the limiting reactant
Any reactant that is left over is the excess reactant

11. If I have 400 tires, 150 engines, 200 steering wheels, and 300 bucket seats (2 per car), how many complete cars could I make?
What is the limiting reactant?
What is excess reactant?

12. S8(l) + 8Cl2(g) → 4S2Cl4(l)
200.0g S and 100.0g Cl2
Determine which is the limiting reactant

13. Percent Yield Reactions do not always produce all of what they should.
____________ yield is how much should be produced based on the limiting reactant
____________ yield is how much is actually produced in an experiment

14. Percent Yield
Percent yield is important in the cost effectiveness of many industrial manufacturing processes.
If you are supposed to make 100 pounds of aspirin, and only produce 50 pounds, the company has now lost money.