Question

Select the answer which shows the correct order, slowest to fastest, of the relative rate of diffusion of the gases.

Answer 1

Diffusion is the process of a substance spreading out to evenly fill its container or environment. Rate of diffusion of a gas is inversely proportional to the molar mass of the gas.

$Rate of diffusion \propto \frac{1}{Molar mass}$

Lighter(lower) the molar mass of the gas , faster will be its rate of diffusion and heavier (higher) the molar mass of the gas , slower will be its rate of diffusion.

We have to arrange the given gases from slowest rate of diffusion to fastest rate of diffusion that means we need to arrange gases from higher molar mass to lower molar mass.

Molar mass of given gases are :

Cl = 35.5 g/mol

Xe = 131.29 g/mol

He = 4.00 g/mol

N = 14.00 g/mol

So correct order for slowest rate of diffusion (highest molar mass) to fastest rate of diffusion (lowest molar mass) is :

Xe , Cl , N , He

Xe having the highest molar mass will have the slowest rate of diffusion and He with lowest molar mass will have the fastest rate of diffusion, so option 'c' is correct.

Note : Slowest rate of diffusion = High Molar Mass

Fastest rate of diffusion = Low Molar Mass