Chemistry - Ideal Gas Question with Solution | TestHub

The rate of diffusion of a gas is inversely proportional to the square root of its molar mass (Graham's Law of Diffusion). For two gases to diffuse at the same rate at the same P and T, their molar masses must be equal.

Molar mass of NO = $14.01+16.00=30.01$ g/mol

Molar mass of C₂H₆ = $2(12.01)+6(1.01)=24.02+6.06=30.08$ g/mol

Since their molar masses are approximately equal, NO and C₂H₆ will diffuse at nearly the same rate.