Molecular Formula Practice Test Questions

Chemistry Test Questions

The molecular formula of a compound is a representation of the number and type of elements present in one molecular unit of the compound. This 10-question practice test deals with finding the molecular formula of chemical compounds.

A periodic table will be required to complete this test. Answers appear after the final question.

Question 1

You can determine molecular formula from the number and type of elements.
You can determine molecular formula from the number and type of elements. Lawrence Lawry/Getty Images

An unknown compound is found to contain 40.0 percent carbon, 6.7 percent hydrogen and 53.3 percent oxygen with a molecular mass of 60.0 g/mol. What is the molecular formula of the unknown compound?

Question 2

A hydrocarbon is a compound comprised of carbon and hydrogen atoms. An unknown hydrocarbon is found to contain 85.7 percent carbon and an atomic mass of 84.0 g/mol. What is its molecular formula?

Question 3

A piece of iron ore is found to contain a compound containing 72.3 percent iron and 27.7 percent oxygen with a molecular mass of 231.4 g/mol. What is the molecular formula of the compound?

Question 4

A compound containing 40.0 percent carbon, 5.7 percent hydrogen and 53.3 percent oxygen has an atomic mass of 175 g/mol. What is the molecular formula?

Question 5

A compound contains 87.4 percent nitrogen and 12.6 percent hydrogen. If the molecular mass of the compound is 32.05 g/mol, what is the molecular formula?

Question 6

A compound with a molecular mass of 60.0 g/mol is found to contain 40.0 percent carbon, 6.7 percent hydrogen, and 53.3 percent oxygen. What is the molecular formula?

Question 7

A compound with molecular mass of 74.1 g/mol is found to contain 64.8 percent carbon, 13.5 percent hydrogen, and 21.7 percent oxygen. What is the molecular formula?

Question 8

A compound is found to contain 24.8 percent carbon, 2.0 percent hydrogen and 73.2 percent chlorine with a molecular mass of 96.9 g/mol. What is the molecular formula?

Question 9

A compound contains 46.7 percent nitrogen and 53.3 percent oxygen. If the molecular mass of the compound is 60.0 g/mol, what is the molecular formula?

Question 10

A gas sample is found to contain 39.10 percent carbon, 7.67 percent hydrogen, 26.11 percent oxygen, 16.82 percent phosphorus, and 10.30 percent fluorine. If the molecular mass is 184.1 g/mol, what is the molecular formula?

Answers

1. C2H4O2
2. C6H12
3. Fe3O4
4. C6H12O6
5. N2H4
6. C2H4O2
7. C4H10O
8. C2H2Cl2
9. N2O2
10. C6H14O3PF

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