DP Physics (last assessment 2024)

Question 21M.2.SL.TZ2.2

Date	May 2021	Marks available	[Maximum mark: 6]	Reference code	21M.2.SL.TZ2.2
Level	SL	Paper	2	Time zone	TZ2
Command term	Calculate, Deduce, Predict	Question number	2	Adapted from	N/A

[Maximum mark: 6]

21M.2.SL.TZ2.2

The graph shows the variation with temperature T of the pressure P of a fixed mass of helium gas trapped in a container with a fixed volume of 1.0 × 10⁻³m³.

(a)

Deduce whether helium behaves as an ideal gas over the temperature range 250 K to 500 K.

[2]

Markscheme

«He behaves as ideal gas if» $p \propto T$ «at constant V» ✓

uses two points to show that $p \propto T$ ✓

MP1 can also be described as $\frac{p}{T} = k OR \frac{p}{T} = \frac{n R}{V}$

(b)

Helium has a molar mass of 4.0 g. Calculate the mass of gas in the container.

[2]

Markscheme

$\frac{100 \times 10^{3} \times 10^{- 3}}{250 \times 8.31} = « 0.048 mol »$ ✓

$« 0.048 \times 4 = » 0.19 « g »$ ✓

Allow any correct data point to be used.

Allow ECF from MP1

(c)

A second container, of the same volume as the original container, contains twice as many helium atoms. The graph of the variation of P with T is determined for the gas in the second container.

Predict how the graph for the second container will differ from the graph for the first container.

[2]

Markscheme

recognizes that pressure will double ✓

graph will be steeper OR gradient will be larger ✓

graph will still go through the origin ✓

MP1 can be expressed as e.g.“ $p \propto n$ ” OR “ $\frac{n R}{V}$ will double”.

Accept $p v = 2 n R T$ for MP1.

Syllabus sections

Core

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

Core » Topic 3: Thermal physics

Question 21M.2.SL.TZ2.2

Select a Test

Syllabus sections

Confirm action