A sample of He gas (2.0 mmol) effused through a pinhole in 53 s. The same amount of an unknown gas, under the same conditions, effused through the pinhole in 248 s. The molecular mass of the unknown gas is _ g/mol.
A) 19
B) 5.5
C) 350
D) 88
E) 0.19

Question

Quizplus · Accepted Answer

The rate of effusion is inversely proportional to the square root of the molar mass (Graham's law). Using the formula (rate1/rate2) = sqrt(M2/M1), where M1 is the molar mass of He (4 g/mol) and M2 is the molar mass of the unknown gas, we find M2 = 88 g/mol.

A Sample of He Gas (2