Analía Bellizzi – Chemistry Classes

Ronald Reagan Senior High School

# Empirical and Molecular Formula Exercises

Exercises – CLASSWORK:

1.  What is the empirical formula for a compound which contains 0.0134 g of iron, 0.00769 g of sulfur and 0.0115 g of oxygen?

2.  Find the empirical formula for a compound which contains 32.8% chromium and 67.2% chlorine.

3.  Which is the emprical formula of the compound that contains 0.463 g Tl (#81),  0.0544 g of carbon,  0.00685 g of hydrogen and 0.0725 g oxygen?

4.  200 g of a compound were analyzed. The student discovered that contains 160.5 g of zinc were present, and the rest was oxygen. Calculate the empirical formula

5. Barry has a sample of a compound which weighs 200 grams and contains only carbon, hydrogen, oxygen and nitrogen.  By analysis, he finds           that it contains 97.56 grams of carbon, 4.878 g of hydrogen, 52.03 g of oxygen and 45.53 g of nitrogen.  Find its empirical formula.

6.  The characteristic odor of pineapple is due to ethyl butyrate, an organic compound which contains only carbon, hydrogen and oxygen.  If a            sample of ethyl butyrate is known to contain 0.62069 g of carbon, 0.103448 g of hydrogen and 0.275862 g of oxygen.

a) what is the empirical formula for ethyl butyrate?

b) Knowing that the molar mass of the compound is 116 g/mol, which is the molecular formula?

7.  250 grams of a compound which contains only carbon, hydrogen and oxygen is analyzed and found to contain the exact same percentage of          carbon as it has oxygen.  The percentage of hydrogen is known to be 5.98823%.  Find the empirical formula of the compound.

8.  Naphthalene is a carbon and hydrogen containing compound often used in moth balls.
The empirical formula is C5H4 and its molar mass is 128.00 g/mol. Find the empirical and molecular formula.

9.  A compound with the following composition has a molar mass of 60.00 g/mol: 39.97% carbon; 13.41% hydrogen; 46.62% nitrogen. Find the empirical and molecular formula.

10. What is the empirical formula for a compound which contains 0.4118 g of iron, 0.2353 g of sulfur and 0.3530 g of oxygen?