IB Physics SL B 3 5 Ideal Gas Equations Questions

Practise IB Physics SL B.3.5 by applying pV=nRT and pV=NkBT to calculate gas pressure, volume, temperature, moles and particles.

Exam points

Apply pV = nRT or pV = NkBT to calculate pressure, volume, temperature, amount of substance, molecule number or gas mass from data, converting temperatures to kelvin.
Use the equation of state to compare gas containers and predict how pressure, volume, temperature and particle number change when stated conditions change.
Interpret pressure–temperature or volume–temperature graphs and proportionalities at fixed conditions to determine ideal-gas behaviour or particle quantities.

[Maximum number: 2]

The equipment shown in the diagram was used by a student to investigate the variation with volume, of the pressure p of air, at constant temperature. The air was trapped in a tube of constant cross-sectional area above a column of oil.

Figure for Question IB Physics SL B 3 5 Ideal Gas Equations Questions question 1 — IB Physics SL

The pump forces oil to move up the tube decreasing the volume of the trapped air.

The cross-sectional area of the tube is $1.3 \times 10^{-3} \mathrm{~m}^{2}$ and the temperature of air is 300 K . Estimate the number of moles of air in the tube.

$n=\frac{b A}{R T} OR$ correct substitution of one point from the graph

$n=\frac{5 \times 10^{4} \times 1.3 \times 10^{-3}}{8.31 \times 300}=0.026 \approx 0.03$

Answer must be to 1 or 2 SF. Allow ECF from (b).

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IB Physics SL B 3 5 Ideal Gas Equations Questions question 1