1. Unit 9: The Mole
Molar Mass Notes

2. What is molar mass? It is the TOTAL mass of the entire compound.
It is the mass of 1 mole of the substance.
Every atom of the compound is calculated into the mass.
It is expressed in grams/mol (g/mol)

3. How is molar mass calculated?
Use the periodic table to determine the mass of a single mole of a substance.
The molar mass comes from the periodic table.
AMU=molar mass
Unit for molar mass is g/mol
Every atom in the compound, has its molar mass added into the overall molar mass of the substance.

4. Find the molar mass: 1. Copper: 6. Sulfur: 2. Aluminum: 7. Oxygen:
3. Hydrogen: Chlorine:
4. Nitrogen: Potassium:
5. Uranium: Beryllium:

5. Determining the molar mass of compounds:
To add up the mass of EVERY atom in the compound, you must remember.
The subscripts represent the number of atoms in a compound
O2 = 2 oxygen atoms
Yes, If there is a coefficient, you multiply the coefficient by the subscript to calculate the number of atoms, but NOT for the molar mass of a substance.
2CaCl2 = 2 calcium and 4 chlorine atoms
The element that the subscript is attached to only applies to that element, unless the subscript is outside parenthesis.
PO4 = 1 phosphorus and 4 oxygen
(PO4)2 = 2 phosphorus and 8 oxygen
2(PO4)2 = 4 phosphorus and 16 oxygen
FOR MOLAR MASS WE ONLY USE SUBSCRIPTS NOT COEFFECIENTS

6. Determining the molar mass of compounds:
Add the molar masses of EVERY atom in the compound together.
Find the molar mass of H2O
H= = (1) x 2 hydrogen atoms g
O=15.994= (16) x 1 oxygen atom g
Molar mass of H2O g/mol
*You can use whole numbers instead of decimals but you will need to round!

7. Number of each type of atom
Find the molar mass:
Compound Name
Compound Formula
Number of each type of atom
Molar Mass (g/mol)
Copper (III) oxide
Sodium phosphate
Aluminum carbonate
Nitrogen Dioxide
Lithium Carbonate
Sulfur trioxide
Calcium sulfide