IB Physics HL B 3 7 Ideal Gas Internal Energy Questions

Practise IB Physics HL B.3.7 by analysing monatomic-gas internal energy, particle kinetic energy and temperature-dependent state changes.

Exam points

Calculate the internal energy of a monatomic ideal gas using U = 3/2 NkBT or U = 3/2 nRT, including particle or amount conversions.
Explain that an ideal gas has negligible intermolecular potential energy, so its internal energy is the total random translational kinetic energy; relate changes in temperature to changes in internal energy.
Use U = 3/2 nRT to interpret an internal-energy–temperature graph and determine the amount of gas from its gradient.

[Maximum number: 2]

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

Calculate, in J , the internal energy of the gas.

For one atom $U=\frac{3}{2}kT$ $U=2.6\times10^{22}\times\frac{3}{2}\times1.38\times10^{-23}\times310=170\ \mathrm{J}$

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IB Physics HL B 3 7 Ideal Gas Internal Energy Questions question 1