Question

A gaseous mixture of O2 and x containing 20% of x, diffused through a small hole in 134 sec while pure O2 takes 124 secs to diffuse through the same hole. Find molecular weight of x.

Answer 1

According to Graham's law of diffusion, rate of diffusion of a gas is inversely proportional to the square root of the mass of the gas.

Rate is inversely proportional to time.

Plugging in the values to calculate X

0.856(Mass of mixture) = 32

Mass of mixture = 37.4 g

The mixture is 20% X and 80 % Oxygen

If we take total number of moles in the mixture as 1.

Moles of Oxygen = 0.80 mol

Mass of Oxygen =

Moles of X = 0.20 mol

Mass of X = 0.20 mol * Molecular weight of X

Mass of mixture = 0.8 * 32 + 0.2 * X

==> 0.8 * 32 + 0.2 * X = 21.9

25.6 + 0.2 X = 37.4

X = 58.9 g/mol