An unknown gas effuses at 0.850 times the effusion rate of nitrogen dioxide, NO2. Estimate the the molar mass of the unknown gas

Respuesta :

Graham's Law, 
Rate 1 / Rate 2 = √[M2/M1] 
Just substitute, remembering M(NO2) = 46 g/mol, 
0.850 = √[46/M1]; 
Solving, M1 = 63.7 g/mole. The other gas could be SO2, which has molecular weight 63.9 g/mole.