The molar mass of an unknown gas was measured by an effusion experiment.It was found that the unknown gas effused at a rate of 2.2 × 10⁻⁶ mol/hr,whereas the nitrogen gas effused at a rate of 3.1 × 10⁻⁶ mol/hr.The molar mass of the gas is _____. A) 24 g/mol B) 40 g/mol C) 14 g/mol D) 33 g/mol E) 56 g/mol

Question

Quizplus · Accepted Answer

We can use Graham's law of effusion to solve this problem:

(rate of unknown gas) / (rate of nitrogen gas) = sqrt(molar mass of nitrogen gas / molar mass of unknown gas)

Plugging in the values given in the problem:

(2.2 x 10^-11 mol/hr) / (3.1 x 10^-11 mol/hr) = sqrt(28.02 g/mol / molar mass of unknown gas)

Solving for the molar mass of the unknown gas:

molar mass of unknown gas = (28.02 g/mol) x (3.1 x 10^-11/2.2 x 10^-11)^2 = 32.7 g/mol

Rounding to the nearest whole number, we get a molar mass of 33 g/mol, which corresponds to choice D.

The Molar Mass of an Unknown Gas Was Measured by an Effusion