Chemistry Name :

Worksheet : Ch. 4 and 7 : Obj. 11-17 #2 Date :

A. Gas problems :

1. What is the volume of 22.56 moles of hydrogen (H2) at STP?

2. How many moles of helium (at STP)will be needed to fill a balloon which has a volume of 1.95 L?

3. A gas consisting of only nitrogen and oxygen atoms has a density of 2.68g/L. Is this gas nitrogen monoxide, nitrogen dioxide, dinitrogen dioxide or dinitrogen monoxide?

B. Percent composition problems :

4. What is the percent composition of a compound which consists of 80.08 g of calcium and 24.0 g of carbon and 95.9 g of oxygen?

5. What is the percent composition of iron(III) hydroxide?

C. Calculation of empirical and molecular formulas.

6. Give the empirical formulas of the following compounds :

a. vitamin C (C6H8O6)

b. glucose (C6H12O6)

c. acetylene (C2H2)

7. Determine the molecular formulas of the following empirical formulas :

a.  CH2 (molar mass = 56.12)

b.  SO2 (molar mass = 192.21 g/mol)

c. C5H11 (molar mass = 142.32)

8. What are the empirical and molecular formulas of a compound which is 84.09 % carbon and 15.91% hydrogen, and has a molar mass of 114.26 g?

9. What are the empirical and molecular formulas of a compound which is 74.92 % carbon, 12.60% hydrogen, and 12.48% oxygen and has a molar mass of 128.24 g?

10. Benzene is a carcinogen that consists of only carbon and hydrogen and is 7.74% hydrogen by mass. The molar mass of benzene is 78.1 g/mol. Determine the empirical and molecular formulas of benzene.

11. A compound that contains only nitrogen and oxygen is 30.4 % nitrogen by mass and has a molar mass of 92 g/mol. What are the empirical and molecular formulas of the compound?

12. A 16.00 gram sample of a compound that contains only carbon and hydrogen is found to contain 13.70 grams of carbon. The molar mass of the compound is 56.12 grams. What are the empirical and molecular formulas of the compound?

Answers : 1. 505 L 2. 0.0871 mol 3. N2O2 4. 40.04% Ca ; 12.0% C ; 48.0% O 5. 52.25% Fe ; 44.91% O ; 2.83% H 6a. C3H4O3 7a. C4H8 7c. C10H22 8. C8H18 9. C8H16O 10. C6H6 11. N2O4 12. C4H8