A Levels Chemistry

Which of the following would behave most like an ideal gas at room temperature?
A carbon dioxide
B helium
C hydrogen
D nitrogen


Choice B is correct because:

Helium (He) behaves most like an ideal gas at room temperature. As a noble gas, it has a complete electron shell, resulting in minimal intermolecular forces between helium atoms. Furthermore, helium has a small atomic size, which allows it to follow the ideal gas law more closely than the other given options.

Choice A is incorrect because:

Carbon dioxide (CO2) has larger molecules compared to helium and exhibits stronger intermolecular forces, specifically London dispersion & permanent dipole forces. These factors cause carbon dioxide to deviate more from ideal gas behaviour than helium.

Choice C is incorrect because:

Hydrogen (H2) behaves more like an ideal gas compared to many other gases, due to its small molecular size and weak intermolecular forces. However, it does not behave as close to an ideal gas as helium does, because helium's noble gas status and complete electron shell lead to even weaker intermolecular forces.

Choice D is incorrect because:

Nitrogen (N2) also behaves more like an ideal gas compared to many other gases, but its molecular size and intermolecular forces (London dispersion forces) are stronger than those of helium. Thus, nitrogen does not resemble an ideal gas as closely as helium does.

States of Matter | 2008 - O/N - 9701/1 | Q7