Worksheet: Mole Fractions from Partial Pressures

In this worksheet, we will practice using Dalton's law to convert between mole fractions and partial pressures.


A gas mixture used for anesthesia contains 2.83 mol oxygen, O2, and 8.41 mol nitrous oxide, NO2. The total pressure of the mixture is 192 kPa.

What are the mole fractions of O2 and NO2?

  • AO2: 0.663, NO2: 0.337
  • BO2: 0.748, NO2: 0.252
  • CO2: 0.252, NO2: 0.748
  • DO2: 0.337, NO2: 0.663

What are the partial pressures of O2 and NO2?

  • AO2: 48.3 kPa, NO2: 144 kPa
  • BO2: 64.6 kPa, NO2: 127 kPa
  • CO2: 127 kPa, NO2: 64.6 kPa
  • DO2: 144 kPa, NO2: 48.3 kPa


A mixture of hydrogen and oxygen gases is explosive if the oxygen content is more than 3.0%mol.  In which of the following oxygen-hydrogen mixtures is the oxygen content closest to this threshold without exceeding it?

  • AA hydrogen partial pressure of 199,000 Pa and an oxygen partial pressure of 6,200 Pa
  • BA total pressure of 59.00 bar and an oxygen partial pressure of 1.500 bar
  • CA hydrogen mass of 2.419 kg and an oxygen mass of 1.120 kg
  • DA total pressure of 34.55 atm and a hydrogen partial pressure of 33.55 atm
  • EA total mass of 921.3 g and an oxygen mass of 307.2 g

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