Worksheet: Empirical and Molecular Formulas

In this worksheet, we will practice using the structure of a compound to determine its empirical and molecular formulas and identify structural isomers.

Q1:

What is the empirical formula of a compound if a sample contains 0.130 g of nitrogen and 0.370 g of oxygen?

  • A N O 3
  • B N O 2
  • C N O 2 3
  • D N O 5
  • E N O 2 5

Q2:

The molecular formula of caffeine is CHNO81042. What is its empirical formula?

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

Q3:

The molecular formula of sucrose is CHO122211. What is its empirical formula?

  • A C H O 1 2 2 2 1 1
  • B C H O
  • C C H O 1 1 / 6 1 1 / 1 2
  • D C H O 2
  • E C H O 2 1 1 5 . 5

Q4:

The molecular formula of hydrogen peroxide is HO22. What is the empirical formula?

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

Q5:

The molecular formula of glucose is CHO6126. What is its empirical formula?

  • A C H O 2
  • B C H O 3 6 3
  • C C H O 6 1 2 6
  • D C H O
  • E C H O 2

Q6:

The molecular formula of ascorbic acid (vitamin C) is CHO686. What is the empirical formula?

  • A C H O 4
  • B C H O 6 8 6
  • C C H O 4 / 3
  • D C H O
  • E C H O 3 4 3

Q7:

A sample of a compound contains 4.27 g of carbon and 5.69 g of oxygen. No other elements are present. Determine the empirical formula of this compound.

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

Q8:

A sample of a compound contains 5.19 g of carbon and 13.84 g of oxygen. No other elements are present. Determine the empirical formula of this compound.

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

Q9:

A sample of a compound contains 14.13 g of carbon and 2.96 g of hydrogen. No other elements are present. What is the empirical formula of this compound?

  • A C H 3 7
  • B C H 2 7
  • C C H 3
  • D C H 2 5
  • E C H 5

Q10:

A sample of a compound contains 19.91 g of carbon and 3.34 g of hydrogen. No other elements are present. What is the empirical formula of this compound?

  • A C H 3
  • B C H 2 3
  • C C H 3 5
  • D C H 2
  • E C H

Q11:

A molecule of the pesticide metaldehyde contains 8 carbon atoms, 16 hydrogen atoms, and 4 oxygen atoms. What is the empirical formula of metaldehyde?

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

Q12:

The structural formula of acetylene is:

What is the empirical formula?

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

What is the molecular formula?

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

Q13:

The structural formula of bromoethene is:

C H Br C H H

Which of the following has the same empirical formula as this compound?

  • A
    C C H H Br H C H C H H H
  • B
    C C C Br C H H C Br C Br H
  • C
    C H Br C C H C H H Br
  • D
    C H C C H C H Br C H Br C H H H H H Br
  • E
    C H H C C H C C Br C H H H Br H Br

Q14:

The structural formula of acetic acid is as shown.

C C O H H H H O

What is its empirical formula?

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

Q15:

The structural formula of ethyl acetate is as shown.

H C C O C C H H H O H H H H

What is its empirical formula?

  • A C H O 4 8 4
  • B C H O 2
  • C C H O 4 8 2
  • D C H O 2 4
  • E C H O 2 4 2

Q16:

The structural formula of acetic acid is as shown.

C C H H H H

What is its empirical formula?

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

What is its molecular formula?

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

Q17:

The structural formula of sulfuric acid is:

S O H O H O O

What is the empirical formula?

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

What is the molecular formula?

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

Q18:

A hydrocarbon is composed of 85.7% carbon and 14.3% hydrogen by mass.

What is its empirical formula?

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

If 1.56 g of the hydrocarbon occupies a volume of 1.00 L at 0.984 atm and 50C. What is its molecular formula?

  • A C H 3 8
  • B C H 2 2
  • C C H 5 1 0
  • D C H 6 1 0
  • E C H 3 6

Q19:

Sodium peroxide has the empirical formula NaO. The chemical formula of sodium peroxide contains twice as many atoms as the empirical formula. What is the chemical formula of sodium peroxide?

  • A ( N a O ) 2
  • B N a O 2 2
  • C N a O 2
  • D 2 N a O
  • E N a O 2

Q20:

What is the molecular formula for chloric acid?

  • A H C l O 4
  • B H C l O
  • C H C l O 3
  • D H C l O 2

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