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Percent Composition by Mass Worksheet
Gen Chem; Coleman
Show all work, including the correct units
Theoretical Percent Composition by Mass
1. What is the percent composition by mass for each element in sodium phosphate, Na3PO4?
2. What is the percent composition by mass for each element in hydrogen peroxide, H2O2?
3. What is the percent composition by mass for each element in carbon dioxide, CO2?
4. What is the percent composition by mass for each element in ammonium sulfate, (NH4)2SO4, which
is used in fertilizers?
5. What is the percent composition by mass for each element in copper (II) bromide, CuBr2 ?
6. What is the percent composition by mass for each element in aspirin, C9H8O4?
7. What is the percent composition by mass for each element in diphosphorous tetrasulfide, P2S4?
8. What is the percent composition by mass for each element in potassium permanganate, KMnO4
Percent composition from mass data
9. A chemist determines that 1.26 g of iron reacts with 0.54 g of oxygen to form rust. What is the
percent composition of each element in the new compound?
10. In the lab, a chemist analyzed a sample of methanol and found that it was made of 6.2 g of
carbon, 4.1 g of hydrogen, and 15.9 g of oxygen. What is the percent composition of each
element?
11. A compound contains 14.4 g of carbon and 3.2 g of hydrogen. What is the percent composition by
mass of each element in the compound?
12. In an experiment, a 4.4 g sample of a compound containing iron and sulfur is chemically
separated into 2.8 g of iron and the remainder was sulfur. What is the percent composition by
mass of each element in the compound?
13. In an experiment, 32.0 grams of oxygen atoms reacts with 80.1 g of calcium to form a new
compound. What is the percent composition by mass of each element in the new compound?
14. A chemist breaks down a 49.57 g sample of a compound into 10.77 g of sodium, 22.43 g of oxygen,
and the rest is chlorine. What is the percent composition by mass of each element in the new
compound?