1. Chemical Formulas

2. Mass Percent Also known as percent composition.
Shows the mass of each element in a compound as a percent of the total mass of the compound.

3. What is the mass percent of each element in carbon dioxide, CO2?
Example
What is the mass percent of each element in carbon dioxide, CO2?
Find the molar mass of the compound.
Find the percent of each element in the compound.

4. More Examples
Find the mass percent of each element in mercury (I) chloride, Hg2Cl2.
Find the mass percent of each element in ethyne, C2H2.
Find the mass percent of each element in aluminum sulfate, Al2(SO4)3.

5. Application
We can use the ratio of mass of one element compared to mass of the whole compound to determine masses of individual elements in a sample.
Ex. Determine the mass of chlorine in grams of sodium chloride, NaCl.

6. More Examples What mass of carbon is present in 13.8 grams of C3H8?
What mass of potassium is present in 45.8 grams of K2SO4?
What mass of oxygen is present in 112 grams of Mg(NO3)2?