Worksheet: Empirical and Molecular Formulas

In this worksheet, we will practice defining, determining, and converting between a compound’s empirical and molecular formulas.

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.

  • AWCl38
  • BWCl4
  • CWCl5
  • DWCl27
  • EWCl25

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 (BO23).

What is the empirical formula of this compound?

  • ABH2
  • BBH4
  • CBH3
  • DBH23
  • EBH

What is the molecular formula of this compound?

  • ABH3
  • BBH23
  • CBH4
  • DBH26
  • EBH28

Q3:

Caffeine has the chemical formula CHNO81042. What is its empirical formula?

  • ACHNO452
  • BCHNO81042
  • CCHNO
  • DCHNO162084
  • ECHNO4522

Q4:

Sodium peroxide has the formula NaO22. What is its empirical formula?

  • ANaO2
  • BNaO44
  • CNaO2
  • DNaO22
  • ENaO

Q5:

The numbers of carbon, hydrogen and oxygen atoms in a molecule are in the ratio 262. What is the empirical formula of this molecule?

  • ACHO262
  • BCHO3
  • CCHO
  • DCHO222
  • ECHO2

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?

  • ACOH2
  • BCOH242
  • CCOH
  • DCOH2
  • ECOH2

Q7:

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

  • AAlI
  • BAlI6
  • CAlI23
  • DAlI3
  • EAlI3

Q8:

At 200C, a compound of silver oxide decomposes to metallic silver and oxygen. A 69.6 g sample of the silver oxide produces 64.8 g of silver. What is the empirical formula of silver oxide?

  • AAgO2
  • BAgO
  • CAgO3
  • DAgO22
  • EAgO2

Q9:

In an experiment, mercury oxide is heated in a container, producing oxygen gas and mercury in its pure elemental form. The results of the experiment are shown below.

Mass of empty containerMass of empty container + mercury oxideMass of container + mercury
30.0 g73.4 g70.2 g

What is the mass of oxygen gas lost?

What is the mass of mercury produced?

What is the empirical formula for the compound of mercury oxide?

  • AHgO3
  • BHgO2
  • CHgO
  • DHgO2
  • EHgO22

Q10:

Ethylene is made entirely of carbon and hydrogen atoms. It has a molar mass of 28 g/mol and contains 85.7% carbon. Determine the empirical formula of ethylene.

  • ACH24
  • BCH4
  • CCH3
  • DCH2
  • ECH

Q11:

A vanadium oxide compound is found to be 68% vanadium and 32% oxygen by mass. What is the empirical formula of this compound? Take the atomic masses of vanadium and oxygen to be 51 and 16, respectively.

  • AVO23
  • BVO49
  • CVO
  • DVO2
  • EVO25

Q12:

Oxalic acid is an organic compound found in many plants, including rhubarb. It is found to contain 26.7% carbon and 71.1% oxygen, with the rest being hydrogen. If the molar mass of oxalic acid is 90 g/mol, what is its molecular formula?

  • ACHO222
  • BCO2
  • CCO22
  • DCHO2
  • ECHO224

Q13:

A compound contains an unknown element, X, and has the empirical formula CHX39. Analysis of the compound shows it contains 50% carbon. What is element X?

  • AChlorine
  • BSilicon
  • CAluminum
  • DCopper
  • EMagnesium

Q14:

A compound with the empirical formula CHNO572 has a molar mass of 339 g/mol. What is the molecular formula of this compound?

  • ACHNO121625
  • BCHNO152136
  • CCHNO101424
  • DCHNO202848
  • ECHNO81035

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