Which set of gases is listed from slowest to fastest diffusion rate?

Question

Quizplus · Accepted Answer

The diffusion rate of a gas is inversely proportional to its molar mass, so the gas with the smallest molar mass will diffuse the fastest. The molar masses of the gases listed from smallest to largest are: He (4 g/mol), HCN (27 g/mol), H₂ (34 g/mol), and O₃ (32 g/mol). Therefore, the order of diffusion rate from fastest to slowest is He > HCN > O₃ > H₂, which is best represented by choice C.

Which Set of Gases Is Listed from Slowest to Fastest