IB Physics HL B 3 5 Ideal Gas Equations Questions

Practise IB Physics HL B.3.5 by combining pV=nRT, pV=NkBT and multi-state gas data in demanding calculation problems.

Exam points

Use PV=nRT or PV=NkBT to calculate pressure, volume, temperature, amount of substance, particle number or gas mass, converting to Kelvin and SI units where required.
Compare gas states, containers and connected systems to predict changes in pressure, volume, temperature, amount or mass when gas is added, removed or redistributed.
Interpret or construct pressure–temperature, volume–temperature and pressure–inverse-volume graphs, using gradients, intercepts and data points to determine gas quantities.
Relate the macroscopic and microscopic forms of the equation of state to particle number, density, molar mass and the force exerted by a gas.

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Study B.3.5—Ideal gas equations conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[Maximum number: 2]

(a)

An ideal monatomic gas is kept in a container of volume $2.1 \times 10^{-4} \mathrm{~m}^{3}$ , temperature 310 K and pressure $5.3 \times 10^{5} \mathrm{~Pa}$ .

[ 1 ]

(i)

Calculate the number of atoms in the gas.

[ 1 ]

$N=\frac{pV}{kT}=\frac{5.3\times10^{5}\times2.1\times10^{-4}}{1.38\times10^{-23}\times310}=2.6\times10^{22}$

(b)

The volume of the gas in (a) is increased to $6.8 \times 10^{-4} \mathrm{~m}^{3}$ at constant temperature.

[ 1 ]

(i)

Calculate, in Pa , the new pressure of the gas.

[ 1 ]

$p_2=5.3\times10^{5}\times\frac{2.1\times10^{-4}}{6.8\times10^{-4}}=1.6\times10^{5}\ \mathrm{Pa}$

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

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