Calculate the molar mass of a gas if equal volumes of nitrogen and the unknown gas take 2.2 and 4.1 minutes, respectively, to effuse through the same small hole under conditions of constant pressure and temperature.

Strategy

Because the rates of effusion are inversely proportional to the square root of the molar masses, we can use the relative rate of effusion of the two gases and the molar mass of one (nitrogen) to calculate the molar mass of the unknown gas.