Kp, Partial Pressures and Gas Equilibria · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Kp from partial pressures

Science · Chemistry · ages 17-18
Name ______________________   Date ____________

  1. How do you turn a mole fraction into a partial pressure?

    • Divide it by the total pressure
    • Multiply by the total pressure
    • Add it to the total pressure

  2. How do you find the mole fraction of a gas in a mixture?

    • Its moles divided by the total moles
    • Its pressure minus the total pressure
    • Its moles times the total moles

  3. Raising the total pressure changes Kp as well as the position of equilibrium.

    Circle one:   True   False

  4. For N2 + 3H2 going to 2NH3, which way does higher total pressure shift the position?

    • Toward the reactants, with more gas moles
    • It stays exactly where it was
    • Toward the products, with fewer gas moles

  5. A vessel holds 2 mol of gas A and 3 mol of gas B at 100 kPa total. What is the partial pressure of A in kPa?

    Answer: ______________

  6. Which Kp expression fits N2 + 3H2 going to 2NH3?

    • p(N2) times p(H2) over p(NH3)
    • p(NH3) squared over p(N2) times p(H2) cubed
    • p(NH3) over p(N2) times p(H2)

  7. A mixture holds 1 mol of A and 4 mol of B at 200 kPa total. What is the partial pressure of B in kPa?

    Answer: ______________

  8. A student says ammonia plants use high pressure because it raises Kp. What is wrong?

    • High pressure lifts yield through position, Kp stays fixed
    • High pressure lowers the yield by shifting position backwards
    • High pressure works by changing the rate equation of the reaction
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Kp from partial pressures W1-mt_1R8BpA2hfK-s1

  1. Multiply by the total pressure · Each gas takes its share of the total, so multiply the fraction by the total pressure.
  2. Its moles divided by the total moles · Mole fraction is that gas over the total. The other options mix up the maths.
  3. False · Pressure shifts the position but Kp only answers to temperature. The sentence is false.
  4. Toward the products, with fewer gas moles · Four gas moles become two, so pressure pushes the system toward the products.
  5. 40 · Mole fraction of A is 2/5 = 0.4, and 0.4 times 100 kPa is 40 kPa.
  6. p(NH3) squared over p(N2) times p(H2) cubed · Products go on top with powers matching the balancing numbers: 2, 1 and 3.
  7. 160 · B owns 4/5 = 0.8 of the mixture, and 0.8 times 200 kPa is 160 kPa.
  8. High pressure lifts yield through position, Kp stays fixed · Pressure moves the position toward fewer moles. Kp only moves with temperature.
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