Lesson 5.1.4

5.1.4 Ideal gases Quiz: OCR Physics, Unit 4

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 5.1.4, Ideal gases: 20 multiple choice questions for the OCR Physics (H156), Unit 4: Newtonian world and astrophysics, written with Revision Ninja.

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The 20 questions

  1. The Avogadro constant N_A is approximately:

    • 6.02 x 10^-23 mol^-1
    • 8.31 J mol^-1 K^-1
    • 6.02 x 10^23 mol^-1
    • 1.38 x 10^-23 J K^-1

  2. 3.0 x 10^24 molecules of gas make up how many moles?

    • 5.0 mol
    • 18 mol
    • 1.8 x 10^48 mol
    • 0.2 mol

  3. Which equation represents the ideal gas equation of state?

    • p/V = nRT
    • pV = nRT
    • pV = nR/T
    • pV = n/RT

  4. A gas at pressure 2.0 x 10^5 Pa occupies 1.0 L at constant temperature. What is its pressure when compressed to 0.5 L?

    • 1.0 x 10^5 Pa
    • 2.0 x 10^5 Pa
    • 1.0 x 10^6 Pa
    • 4.0 x 10^5 Pa

  5. At constant volume, a gas has pressure 100 kPa at 300 K. What is its pressure at 600 K?

    • 50 kPa
    • 400 kPa
    • 100 kPa
    • 200 kPa

  6. In the ideal gas model, what is assumed about the volume of individual molecules?

    • Variable
    • Maximum
    • Constant
    • Negligible

  7. In the kinetic model, collisions between molecules and container walls are:

    • perfectly elastic
    • always sticky
    • absent
    • perfectly inelastic

  8. In the kinetic theory equation p = 1/3 rho <c^2>, what does <c^2> represent?

    • Mean square speed
    • Average speed
    • Root mean speed
    • Maximum velocity

  9. How is root mean square speed mathematically calculated from mean square speed?

    • Divide by two
    • Square
    • Square root
    • Cube root

  10. The Boltzmann constant k is defined as:

    • R/N_A
    • nR/T
    • R x N_A
    • N_A/R

  11. Using R = 8.31 J mol^-1 K^-1 and N_A = 6.02 x 10^23 mol^-1, what is the Boltzmann constant?

    • 1.38 x 10^-23 J K^-1
    • 6.02 x 10^23 J K^-1
    • 8.31 x 10^-23 J K^-1
    • 1.38 x 10^23 J K^-1

  12. One mole of gas at 273 K occupies 0.0224 m^3. What is its pressure?

    • 2.3 x 10^3 Pa
    • 1.0 x 10^3 Pa
    • 1.0 x 10^7 Pa
    • 1.0 x 10^5 Pa

  13. The mean translational kinetic energy of a molecule of an ideal gas at 300 K is approximately:

    • 4.1 x 10^-21 J
    • 9.3 x 10^-21 J
    • 6.2 x 10^-21 J
    • 1.4 x 10^-23 J

  14. Oxygen molecules have mass 5.3 x 10^-26 kg at 300 K. What is their r.m.s. speed (c = sqrt(3kT/m))?

    • 300 m/s
    • 484 m/s
    • 1.2 x 10^-20 m/s
    • 2.3 x 10^5 m/s

  15. 2.0 mol of ideal gas at 300 K is in a volume of 0.040 m^3. What is the pressure?

    • 8.3 x 10^2 Pa
    • 1.2 x 10^4 Pa
    • 1.2 x 10^5 Pa
    • 2.5 x 10^6 Pa

  16. At what temperature does the extrapolated pressure of a constant-volume ideal gas equal zero?

    • Freezing point
    • Absolute zero
    • Boiling point
    • Triple point

  17. If the absolute temperature of an ideal gas is doubled, by what factor does r.m.s. speed increase?

    • √2
    • 0.5
    • 4
    • 2

  18. N molecules are in volume V. If N and V are both doubled at the same molecular speeds, the pressure:

    • quadruples
    • doubles
    • is unchanged
    • halves

  19. From pV = Nm<c^2>/3 and pV = NkT, the mean translational kinetic energy per molecule is:

    • 3kT/2
    • 2kT/3
    • 3kT
    • kT/2

  20. What thermodynamic quantity determines the total internal energy of a fixed mass of ideal gas?

    • Absolute temperature
    • Pressure
    • Density
    • Volume

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