Section 10.2

Section 10.2

Molar Mass of Compounds

We find the molar mass of an element from its value on the periodic table

—We also work with compounds

—For example- 1.29 mol of water = ? g

—We need to know how much 1 mole of water weighs

To find the molar mass of a compound:

• Determine the number of atoms of each element in the compound

• Multiply this number by the average atomic mass (# on the Periodic Table) of each corresponding element.

• Add together the totals for each element.

For Water:

• —2 atoms of H at 1.0079 g = 2.0158 g

• —1 atom of O at 15.999 g = 15.999 g

• —2.0158 g + 15.999 g = 18.015 g (molar mass of H2O)