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Chemical Equilibria

Partial Pressures and Mole Fractions

  • 3 things to know
  • Papers 1, 2 and 3

Overview

Mole fraction, partial pressure, and calculating both from a gas mixture.

What you need to know

Answer each one before you reveal it.

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Key term

What are partial pressure and mole fraction?

Key term

What is the partial pressure of a gas in a mixture?

Key term

What is the mole fraction of a gas in a mixture?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the partial pressure of a gas in a mixture?

    Model answer

    The pressure that a gas would exert if it alone occupied the total volume of the mixture at the same temperature.

  2. 2

    What is the mole fraction of a gas in a mixture?

    Model answer

    The ratio of the number of moles of that gas to the total number of moles of all gases in the mixture.

  3. 3

    How do you calculate the mole fraction of a gas?

    Model answer

    Mole fraction = moles of the gas ÷ total moles of all gases in the mixture.

  4. 4

    What is the relationship between partial pressure, mole fraction, and total pressure?

    Model answer

    Partial pressure = mole fraction × total pressure.

  5. 5

    What is the sum of all mole fractions in a gas mixture?

    Model answer

    The sum of all mole fractions equals 1.

  6. 6

    If a gas mixture contains 2 mol of gas A and 3 mol of gas B at a total pressure of 100 kPa, what is the mole fraction of gas A?

    Model answer

    Mole fraction of A = 2 ÷ (2 + 3) = 0.4.

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The sum of all mole fractions equals 1.
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