1. Unit 5: Stoichiometry
Moles and Molar Mass

2. The Mole 1 dozen = 12 eggs 1 ream = 500 sheets of paper
1 hat trick = 3 goals
1 mole = x 1023 of something
Or 602,200,000,000,000,000,000,000
Also known as “Avogadro’s number”

3. The Mole 1 mole of hydrogen = 6.022 x 1023 atoms
1 mole of carbon = x 1023 atoms
1 mole of gold = x 1023 atoms
1 mole of calcium = x 1023 atoms
See the pattern?

4. Understanding Check
Suppose we invented a new collection unit called a “mep”. One mep contains 8 objects.
A. How many paper clips in 1.0 mep?
B. How many oranges in 2.0 meps?
C. How many meps contain 40 gummy bears?

5. Molar Mass 1 mole of C atoms = 12.011 g 1 mole of Mg atoms = 24.305 g
Molar mass: number of grams of one mole of an element or compound
1 mole of C atoms = g
1 mole of Mg atoms = g
1 mole of Cu atoms = g
What is the molar mass of the following?
1 mole of Br atoms?
1 mole of Sn atoms?

6. Molar Mass of Compounds
We can also find the molar mass of compounds by ADDING the molar masses of each element
Molar masses have units of g/mol
Questions to ask yourself:
1. How many of each atom?
2. Molar mass of each element?
3. Total mass from each element?
Then add them all together!

7. Molar Mass of Compounds Example #1
Find the molar mass of magnesium chloride, MgCl2
Questions to ask yourself:
1. How many of each atom?
2. Molar mass of each element?
3. Total mass from each element?
Then add them all together!

8. Molar Mass of Compounds Example #2
Find the molar mass of calcium hydroxide
Questions to ask yourself:
1. How many of each atom?
2. Molar mass of each element?
3. Total mass from each element?
Then add them all together!

9. Molar Mass Practice

10. More Practice with Molar Mass
For each of the compounds below, determine the number of atoms for each element:
1. Cu3PO4
2. Fe2(SO2)3
3. potassium phosphide
Used as a quick review on Day 2

11. Practice with Molar Mass
For each of the compounds below, determine the molar mass of the compound:
1. MnBr2
2. Sr(NO3)2
Used as a quick review on Day 2

12. Calculations with Molar Mass
Grams Moles

13. The Box! Grams (g) Molar Mass (g/mol) Moles (mol) down = divide
up = multiply

14. Converting Grams to Moles
Aluminum is often used for the structure of light-weight bicycle frames. How many moles of Al are in 81.0 grams of Al?
81.0 grams Al = ? moles Al
Use the box method!
grams
81.0 g
molar mass
g/mol
moles
down = divide
down = divide

15. Converting Grams to Moles Practice
How many moles does a 25.2 gram sample of CaCl2 contain?
grams
molar mass
moles

16. Converting Moles to Grams
The decomposition of hydrogen peroxide (H2O2) provides sufficient energy to launch a rocket. How many grams of H2O2 are needed for rocket launch that requires 5.00 moles H2O2?
5.00 moles H2O2 = ? g H2O2
Use the box method!
grams
molar mass
g/mol
moles
5.00 moles
up = multiply

17. Converting Moles to Grams Practice
Aluminum satellite dishes are resistant to corrosion because the aluminum reacts with oxygen in the air to form a coating of aluminum oxide (Al2O3). This tough, resistant coating prevents any further corrosion. What is the mass of 9.45 mol of Al2O3?
grams
molar mass
moles