How can I calculate the molar mass of a compound?

May 5, 2014

The molar mass is the combined atomic masses of the elements of the compound. This is referred to as the gram formula mass or the molar mass.

We can complete an example using the molecule Copper (II) Chloride.

Copper (II) Chloride or $C u C {l}_{2}$

There is one atom of copper for every two atoms of chlorine in this molecule.

We will find the molar mass (gfm) of the molecule.

copper has a mass of 63.5 amu (from the periodic able)
chlorine has a mass of 35.45 amu (from the periodic table)

Cu 1 x 63.5 = 63.5
Cl 2 x 35.45 = 70.9

63.5 + 70.9 = 134.4 $\frac{g}{m o l}$ is the molar mass of Copper (II) Chloride.

Lets complete a second example using Glucose.

Glucose is ${C}_{6} {H}_{12} {O}_{6}$

To begin we need to find the molar mass (gram formula mass of the glucose molecule.

carbon has a mass of 12.01 amu (mass from the periodic table)
hydrogen has a mass of 1.01 amu
oxygen has a mass of 15.99 amu

C 6 x 12.01 = 72.06 (atom number x amu)
H 12 x 1.01 = 12.12
O 6 x 15.99 = 95.94

72.06 + 12.12 + 95.94 = 180.12 $\frac{g}{m o l}$ is the molar mass of Glucose.