Percent composition is calculated by finding the molar mass of a compound using the periodic table, determining the mass contributed by the component of interest, and dividing that mass by the total molar mass of the compound before multiplying by 100. This allows you to determine the percentage of a compound's total mass made up of a particular component by mass. The document provides an example calculating the percent composition of carbon in carbon dioxide (CO2).

1. Percent Composition
of Compounds

2. Percent Composition
The percent composition of a
component in a compound is
the percent of the total mass of
the compound that is due to
that component.

3. Find the molar mass of the
compound by adding up the masses
of each atom in the compound
using the periodic table.

4. Calculate the mass due to the component in
the compound you are solving by adding up
the mass of these atoms.
Divide the mass due to the component by the
total molar mass of the compound and
multiply by 100.

5. Percent Composition = Mass due to specific component X 100
Total molar mass of compound

6. Calculate the percent composition of carbon in
each of the following:
 CO2
 12.1 + 2 (16.OO) = 44.01 g/mol
Carbon oxygen CO2
12.01 g/mol X 10o = 27.29 %
44.01g/mol