Worksheet: Empirical and Molecular Formulas

In this worksheet, we will practice defining and converting between the empirical, molecular, and structural formulas of a compound.

Q1:

A compound containing only tungsten and chlorine is reduced with hydrogen to produce hydrogen chloride gas and 0.2232 g of tungsten metal. Complete reaction of the hydrogen chloride in water requires 46.2 mL of a 0.1051 M sodium hydroxide solution. Determine the empirical formula of the unknown compound.

  • A W C l 4
  • B W C l 5
  • C W C l 3 8
  • D W C l 2 7
  • E W C l 2 5

Q2:

A compound composed of boron and hydrogen has a molar mass of approximately 28 g/mol. A sample of the compound weighing 25.0 mg burns in air to produce 63.0 mg of boron oxide ( B O 2 3 ).

What is the empirical formula of this compound?

  • A B H
  • B B H 2 3
  • C B H 3
  • D B H 2
  • E B H 4

What is the molecular formula of this compound?

  • A B H 3
  • B B H 4
  • C B H 2 6
  • D B H 2 3
  • E B H 2 8

Q3:

Caffeine has the chemical formula C H N O 8 1 0 4 2 . What is its empirical formula?

  • A C H N O 4 5 2
  • B C H N O 8 1 0 4 2
  • C C H N O 1 6 2 0 8 4
  • D C H N O
  • E C H N O 4 5 2 2

Q4:

Sodium peroxide has the formula N a O 2 2 . What is its empirical formula?

  • A N a O 4 4
  • B N a O 2
  • C N a O
  • D N a O 2
  • E N a O 2 2

Q5:

The numbers of carbon, hydrogen and oxygen atoms in a molecule are in the ratio 2 6 2 . What is the empirical formula of this molecule?

  • A C H O 2
  • B C H O 2 2 2
  • C C H O 2 6 2
  • D C H O
  • E C H O 3

Q6:

In a chemical compound containing carbon, oxygen and hydrogen, there are equal numbers of carbon and hydrogen atoms. However, the number of oxygen atoms is twice the number of hydrogen atoms. What is the empirical formula of the compound?

  • A C O H 2 4 2
  • B C O H
  • C C O H 2
  • D C O H 2
  • E C O H 2

Q7:

What is the average oxidation state of chlorine in chlorine perchlorate ( C l O ) 2 4 ?

O Cl O O O Cl
  • A+4
  • B+2.5
  • C+4.5
  • D+3
  • E+3.5

Q8:

A binary compound is produced by the reaction of aluminum and iodine. What is the empirical formula of this compound?

  • A A l I 3
  • B A l I
  • C A l I 3
  • D A l I 6
  • E A l I 2 3

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