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 of it contains 0.130 g of nitrogen and 0.370 g of oxygen?

  • ANO25
  • BNO5
  • CNO3
  • DNO23
  • ENO2

Q2:

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

  • ACHNO81042
  • BCHNO452
  • CCHNO
  • DCHNO1.250.50.25

Q3:

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

  • ACHO122211
  • BCHO
  • CCHO11/611/12
  • DCHO2
  • ECHO2115.5

Q4:

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

  • AHO2
  • BHO22
  • CHO
  • DHO2

Q5:

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

  • ACHO2
  • BCHO363
  • CCHO6126
  • DCHO
  • ECHO2

Q6:

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

  • ACHO4
  • BCHO343
  • CCHO686
  • DCHO4/3
  • ECHO

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.

  • ACO2
  • BCO
  • CCO2
  • DCO3
  • ECO23

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.

  • ACO
  • BCO2
  • CCO3
  • DCO2
  • ECO23

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?

  • ACH37
  • BCH27
  • CCH3
  • DCH25
  • ECH5

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?

  • ACH3
  • BCH23
  • CCH35
  • DCH2
  • ECH

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?

  • ACHO24
  • BCHO42
  • CCHO8164
  • DCHO28
  • ECHO22

Q12:

The structural formula of acetylene is as shown. HCCH

What is its empirical formula?

  • ACH2
  • BCH24
  • CCH
  • DCH32
  • ECH22

What is the molecular formula?

  • ACH22
  • BCH
  • CCH32
  • DCH24
  • ECH2

Q13:

The structural formula of bromoethene is as shown.

CHBrCHH

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

  • A
    CHBrCCHCHHBr
  • B
    CHCCHCHBrCHBrCHHHHHBr
  • C
    CCHHBrHCHCHHH
  • D
    CCCBrCHHCBrCBrH
  • E
    CHHCCHCCBrCHHHBrHBr

Q14:

The structural formula of acetic acid is as shown.

CCOHHHHO

What is its empirical formula?

  • ACHO4
  • BCHO222
  • CCHO242
  • DCHO2
  • ECHO

Q15:

The structural formula of ethyl acetate is as shown.

HCCOCCHHHOHHHH

What is its empirical formula?

  • ACHO484
  • BCHO2
  • CCHO482
  • DCHO24
  • ECHO242

Q16:

The structural formula of acetic acid is as shown.

CCHHHH

What is its empirical formula?

  • ACH
  • BCH2
  • CCH4
  • DCH24

What is its molecular formula?

  • ACH24
  • BCH4
  • CCH2
  • DCH

Q17:

The structural formula of sulfuric acid is as shown.

SOHOHOO

What is its empirical formula?

  • AHSO2
  • BHSO
  • CHSO24
  • DHSO22
  • EHSO2

What is its molecular formula?

  • AHSO22
  • BHSO
  • CHSO24
  • DHSO2
  • EHSO2

Q18:

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

What is its empirical formula?

  • ACH
  • BCH2
  • CCH2
  • DCH3
  • ECH4

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?

  • ACH38
  • BCH22
  • CCH510
  • DCH610
  • ECH36

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(NaO)2
  • BNaO22
  • CNaO2
  • D2NaO
  • ENaO2

Q20:

What is the molecular formula for chloric acid?

  • AHClO4
  • BHClO
  • CHClO3
  • DHClO2

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