Percentage Composition & Molecular Worksheets

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  • Topic: Oxygen, Mole, Chemical formula
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Percent Composition and Molecular Formula Worksheet

1. What’s the empirical formula of a molecule containing 65.5% carbon, 5.5% hydrogen, and 29.0% oxygen? 2. If the molar mass of the compound in problem 1 is 110 grams/mole, what’s the molecular formula? 3. What’s the empirical formula of a molecule containing 18.7% lithium, 16.3% carbon, and 65.0% oxygen? 4. If the molar mass of the compound in problem 3 is 73.8 grams/mole, what’s the molecular formula?

Write the molecular formulas of the following compounds:

5. A compound with an empirical formula of C2OH4 and a molar mass of 88 grams per mole. 6. A compound with an empirical formula of C4H4O and a molar mass of 136 grams per mole. 7. A compound with an empirical formula of CFBrO and a molar mass of 254.7 grams per mole. 8. A compound with an empirical formula of C2H8N and a molar mass of 46 grams per mole.

Answer the following questions:

9. The percentage composition of acetic acid is found to be 39.9% C, 6.7% H, and 53.4% O. Determine the empirical formula of acetic acid. 10. The molar mass for question #9 was determined by experiment to be 60.0 g/mol. What is the molecular formula? 11. Aniline, a starting material for urethane plastic foams, consists of C, H, and N. Combustion of such compounds yields CO2, H2O, and N2 as products. If the combustion of 9.71 g of aniline yields 6.63 g H2O and 1.46 g N2, what is its empirical formula? 12. The molar mass of aniline is 93 g/mol. What is its molecular formula? 13. Calculate the mass percent of carbon, nitrogen and oxygen in acetamide, C2H5NO. 14. A 50.51 g sample of a compound made from phosphorus and chlorine is decomposed. Analysis of the products showed that 11.39 g of phosphorus atoms were produced. What is the empirical formula of the compound? 15. When 2.5000 g of an oxide of mercury, (HgxOy) is decomposed into the elements by heating, 2.405 g of mercury are produced. Calculate the empirical formula. 16. The compound benzamide has the following percent composition. What is the empirical formula? C = 69.40 % H= 5.825 % O = 13.21 % N= 11.57 %

17. A component of protein called serine has an approximate molar mass of 100 g/mole. If the percent composition is as follows, what is the empirical and molecular formula of serine?

C = 34.95 % H= 6.844 % O = 46.56 % N= 13.59 %

Percent Composition and Molecular Formula Worksheet Key

1. What’s the empirical formula of a molecule containing 65.5% carbon, 5.5% hydrogen, and 29.0% oxygen? C3H3O mass = 55 g/mole 2. If the molar mass of the compound in problem 1 is 110 grams/mole, what’s the molecular formula? C6H6O2 3. What’s the empirical formula of a molecule containing 18.7% lithium, 16.3% carbon, and 65.0% oxygen? Li2CO3 4. If the molar mass of the compound in problem 3 is 73.8 grams/mole, what’s the molecular formula? Li2CO3

Write the molecular formulas of the following compounds:

5. A compound with an empirical formula of C2OH4 and a molar mass of 88 grams per mole. C4O2H8 6. A compound with an empirical formula of C4H4O and a molar mass of 136 grams per mole. C8H8O2 7. A compound with an empirical formula of CFBrO and a molar mass of 254.7 grams per mole. C2F2Br2O2 8. A compound with an empirical formula of C2H8N and a molar mass of 46 grams per mole. C2H8N

Answer the following questions:

9. The percentage composition of acetic acid is found to be 39.9% C, 6.7% H, and 53.4% O. Determine the empirical formula of acetic acid. CH2O 10. The molar mass for question #9 was determined by experiment to be 60.0 g/mol. What is the molecular formula? C2H4O2 11. Aniline, a starting material for urethane plastic foams, consists of C, H, and N. Combustion of such compounds yields CO2, H2O, and N2 as products. If the combustion of 9.71 g of aniline yields 6.63 g H2O and 1.46 g N2, what is its empirical formula? C6H7N 12. The molar mass of aniline is 93...
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