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Date November 2021 Marks available 2 Reference code 21N.2.SL.TZ0.2
Level Standard level Paper Paper 2 Time zone 0 - no time zone
Command term Sketch Question number 2 Adapted from N/A

Question

A quantity of 0.24 mol of an ideal gas of constant volume 0.20 m3 is kept at a temperature of 300 K.

State what is meant by the internal energy of an ideal gas.

[1]
a.

Calculate the pressure of the gas.

[1]
b.i.

The temperature of the gas is increased to 500 K. Sketch, on the axes, a graph to show the variation with temperature T of the pressure P of the gas during this change.

[2]
b.ii.

A container is filled with 1 mole of helium (molar mass 4 g mol−1) and 1 mole of neon (molar mass 20 g mol−1). Compare the average kinetic energy of helium atoms to that of neon atoms.

[2]
c.

Markscheme

the total «random» kinetic energy of the molecules/atoms/particles ✓

a.

p=«nRTV=0.24×8.31×3000.20=»3.0×103«Pa» ✓

b.i.

straight line joining (300, 3) and (500, 5) ✓

drawn only in the range from 300 to 500 K ✓

 

Allow ECF from (b)(i) for incorrect initial pressure.
Allow tolerance of ± one grid square for the endpoints.

b.ii.

temperature is the same for both gases ✓

«average» kinetic energy is the same «because Ek=32kT  OR  Ek depends on T only» ✓


Award [1 max] for a bald statement that kinetic energy is the same.

c.

Examiners report

[N/A]
a.
[N/A]
b.i.
[N/A]
b.ii.
[N/A]
c.

Syllabus sections

Core » Topic 3: Thermal physics » 3.2 – Modelling a gas
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