UNIT 5A
Chapter 10: Chemical Quantities
Molar Mass
Mrs. Mansberger
What is Molar Mass?

Element: The atomic mass of an element
expressed in grams is the mass of one
mole of the element.


Example:
16.0 g Oxygen = 1 mol Oxygen
12.0 g Carbon = 1 mol Carbon
With your partner, find the molar masses of the
following elements…
35.5 g/mole
 Chlorine
 Sodium
23.0 g/mole
 Iron
55.8 g/mole

Compound: The sum of the atomic
masses of each atom in the compound.

Example: SO3
Find the molar masses of each element.
Then multiply by the number of atoms of
each element.
Finally, add the masses together.
S = 32.1 g X 1 = 32.1 g
O = 16.0 g X 3 = 48.0 g
80.1g/mole
OR 80.1 g SO3 = 1 mol SO3
Find the Molar Mass
of a Compound
Find the molar mass of aluminum sulfate: Al2(SO4)3
Al = 27.0 g X 2 = 54.0 g
S = 32.1 g X 3 = 96.3 g
O = 16.0 g X 12 = 192 g
+
342 g/mole
OR 342 g Al2(SO4)3 = 1 mol Al2(SO4)3
Try these with your partner…
Find the molar mass of PCl3
P = 31.0 g X 1 = 31.0 g
Cl = 35.5 g X 3 = 107 g
+
138 g PCl3 =
1 mol PCl3
138
g/mole
Find the molar mass of H2CO3
H = 1.0 g X 2 = 2.0 g
C = 12.0 g X 1 = 12.0 g
O = 16.0 g X 3 + = 48.0 g
62.0g/mole
62.0 g H2CO3 =
1 mol H2CO3