1. Zumdahl- Chemistry (5th ed.)
Chapter 3
Stoichiometry
Zumdahl- Chemistry (5th ed.)
Last revision Fall 2006

2. The Mole
The mole is a quantity of matter. It is a count of how many atoms are in a sample.
1 dozen = 12 eggs is like 1 mole = 6.02x1023 particles
Converting between moles and particles is just like doing a dimensional analysis problem.
Particles is a generic term used to stand for:
atoms, molecules, formula units, ions, electrons, etc.

3. Molar Mass
A substance’s molar mass (molecular weight) is the mass in grams of one mole of the compound.
It turns out the molar mass is equivalent to the average atomic mass.
Average atomic mass = amu= g/mol
 g = 1 mole of Carbon C 6
12.011
Formula mass: the mass of all the atoms in a formula

4. Percent Composition Mass percent of an element:
For iron in iron (III) oxide, (Fe2O3)

5. The equation is balanced.
Stoichiometry allows chemists to calculate quantities of different substances in the reaction using their coefficients.
C2H5OH + 3O2  2CO H2O
The equation is balanced.
1 mole of ethanol reacts with 3 moles of oxygen
to produce 2 moles of carbon dioxide and 3 moles of water
The relationship between the substances is called the molar ratio.

6. Limiting Reactant
You can make cookies until you run out of one of the ingredients.
Once this family runs out of sugar, they will stop making cookies (at least any cookies you would want to eat).
4 sticks of butter
7 cups of sugar
30 cups of Milk
24 cups of flour
20 eggs
Cookie Recipe:
½ stick of butter 2 eggs
1 cup sugar cup mikk
3 cups flour

7. Theoretical yield vs. actual yield
The theoretical yield is the maximum amount of product that can be made by the limiting reagent.
In other words it’s the amount of product possible as calculated through the stoichiometry problem.
This is different from the actual yield, which is the amount one actually produces and measures in the lab.

8. Percent Yield Actual Yield Theoretical Yield Percent Yield = x 100
One finds the percent yield by comparing the amount actually obtained (actual yield) to the amount it was possible to make (theoretical yield).
Actual Yield
Theoretical Yield
Percent Yield = x 100