Question

How is Graham's Law of Diffusion calculated?

Answer 1

Explanation:

Graham’s law of diffusion states that the rate of diffusion of a gas at a given temperature is inversely proportional to the square root of its molecular mass, m.

I.e. R α 1/√m

Also, vapour density (ρ) = molar mass (g)/molar volume (v)

Molar mass = vapor density (ρ) x molar volume (v)

Therefore, R α 1/√ρv

For two gases with molecular masses m1 and m2 ; and rates of diffusion R1 and R2:

R1/R2 = √m2/√m1 – (1)

R1/R2 = √ρ2v2 /√ρ1v1 – (2)

Also, rate of diffusion = volume/time I.e. the greater the rate, the shorter the time.

Comparing the rates of diffusion of equal volumes of two gases in times t1 and t2, we have R1 = V/t1 and R2 = V/t2