IB Physics SL B.3.5 Ideal gas equations Question Bank

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

Rearrange pV=nRT or pV=NkBT after converting pressure, volume and temperature to SI units.
Solve multistep gas problems for pressure, volume, temperature, moles or particle number with units.

[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 B.3.5—Ideal gas equations 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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B.3.5—Ideal gas equations question 1