In this video you'll learn to calcuate the percent composition by mass of chemical compounds. Percent composition is a common type of problem found in chemistry courses and one you should be able to quickly solve.

- Find the molar mass for each group of elements in the compound (e.g. all three H atoms in H
_{3}PO_{4}). - Find the molar mass for the entire compound.
- Divide the mass for total mass for each element by the mass of the entire compound. Multiply by 100 to get percent.

Remember, you're finding the percent composition of each element in the compound, one element at a time.

This is a general formula for finding percent composition.

The molar mass of the element means the molar mass for the *total* number of that element in the compound. For example, in
H_{2}O_{2} we would find the molar mass of H and then multiply by "2" since there are two Hydrogen atoms.