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WS 4.1: Percent Composition & Formulas
AP Chemistry
1. In 1987 the first substance to act as s superconductor at a temperature above that of liquid nitrogen (77 K) was
discovered. The approximate formula of this substance YBa2Cu3O7. Calculate the percent composition by mass of this
substance.
2. Hemoglobin is the protein that transports oxygen in mammals. Hemoglobin is 0.347% Fe by mass, and each hemoglobin
molecule contains four iron atoms. Calculate the molar mass of hemoglobin.
3. The most common form of nylon (nylon-6) is 63.68% carbon, 12.38% nitrogen, 9.80% hydrogen, and 14.14% oxygen.
Calculate the empirical formula for nylon-6.
4. The compound adrenaline contains 56.79% C, 6.56% H, 28.37% O, and 8.28 %N by mass. What is the empirical formula
for adrenaline?
5. Adipic acid is an organic compound composed of 49.31% C, 43.79% O, and the rest hydrogen. If the molar mass of
adipic acid is 146.1 g/mol, what are the empirical and molecular formulas of adipic acid?
6. Terephthalic acid is an important chemical used in the manufacture of polyesters and plasticizers. It contains only C, H,
and O. Combustion of 19.81 mg terephthalic acid produces 41.98 mg CO2 and 6.45 mg H2O. If 0.250 mole of
terephthalic acid has a mass of 41.5 g, determine the molecular formula for terephthalic acid.
