CH 6.4 Molar Mass
Molar Mass (M): is the mass in grams of 1 mole or 6.02 x 1023 entities of that substance.
The unit for molar mass is, g/mol.


One mole of an element has a mass expressed in grams which is numerically equivalent to the
element’s average atomic mass expressed in atomic mass units.
Use the periodic table to find the mass of one mole of an element.
Molar Masses of Element
Element
Neon, Ne
Calcium, Ca
Oxygen, O2
Phosporus, P4
Average atomic mass
(u)
20.18
40.08
16.00
30.97
Molar mass (g/mol)
Number of entities
20.18
40.08
32.00
123.9
6.02 x 1023
6.02 x 1023
6.02 x 1023
6.02 x 1023
Molar Masses of Compounds
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The molar mass of a compound is the sum of the molar masses of each entity in the
compound.
Example 1: Calculate the molar mass of carbon dioxide.
Example 2: Calculate the molar mass of iron (III) oxide.
Example 3: Calculate the molar mass of copper(II) chloride hexahydrate.
PRACTICE: p.275 #1 a-g
Calculations Involving Molar Masses
The formula which mathematically connects the amount in moles (n), to the mass in grams (m), to the
molar mass (M) is;
Where, n = amount of entities, in mol
m = mass, in grams
M = molar mass, in g/mol
Example 1: According to the manufacturer, a typical can of cola contains 40.0g of
sucrose, C12H22O11. Calculate the amount of sucrose, in moles in a can of pop.
PRACTICE: p.277 #1 & 2
HOMEWORK: p.277 #4-11