For which of the following gases would you expect Z, the compression factor,
To be greater than one at low pressures?
A) hydrogen
B) methane
C) ethane
D) All gases have Z less than 1 at low pressure.

Question

Quizplus · Accepted Answer

At low pressures, the particles of a gas are far apart from each other and do not interact much. Hence, the gas behaves almost as an ideal gas. However, if the intermolecular forces between the particles are strong, then the gas molecules will attract each other, leading to a lower pressure than would be predicted by an ideal gas law. This will cause Z to be greater than one. Hydrogen is a gas with weak intermolecular forces, so Z will be greater than one at low pressures. Methane and ethane have stronger intermolecular forces, but at low pressures, they still behave as ideal gases, so Z is less than one for them. Therefore, the correct answer is A.

For Which of the Following Gases Would You Expect Z