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Thermal physics (A-level only)

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Question 33

A scientific payload designed to simulate the upper atmosphere of a gas giant contains a gaseous mixture of helium atoms and xenon atoms inside a rigid titanium container. The mixture is in thermal equilibrium at a temperature of 260 K260\text{ K}260 K.

1.

State the relationship between the mean kinetic energies of the helium atoms and the xenon atoms in this mixture.

[1]
2.

Calculate the root mean square speed (crmsc_{\text{rms}}crms​) of the helium atoms.

  • Molar mass of helium = 4.0×10−3 kg mol−14.0 \times 10^{-3}\text{ kg mol}^{-1}4.0×10−3 kg mol−1
  • Universal gas constant R=8.31 J mol−1 K−1R = 8.31\text{ J mol}^{-1}\text{ K}^{-1}R=8.31 J mol−1 K−1
  • Avogadro constant NA=6.02×1023 mol−1N_{\text{A}} = 6.02 \times 10^{23}\text{ mol}^{-1}NA​=6.02×1023 mol−1
  • Boltzmann constant kB=1.38×10−23 J K−1k_{\text{B}} = 1.38 \times 10^{-23}\text{ J K}^{-1}kB​=1.38×10−23 J K−1
[3]
3.

Explain, in terms of the kinetic theory model, how increasing the temperature of the gas mixture increases the pressure it exerts on the container walls.

[4]

Thermal physics (A-level only) Questions

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