Graham's Law: Understanding the Rate of Diffusion of Gases

What is Graham's law?

Graham’s law provides that the rate of diffusion of any gas is inversely proportional to the square root of its molecular weight of that gas.

Graham's Law Explanation

According to Graham’s Law, the rate of diffusion of gas is inversely proportional to the square root of its molecular mass. Therefore, molecules of gas with lower molecular mass at constant temperature and pressure will diffuse faster than the molecules with higher molecular mass. The mathematical formula to compare the rates of two different gases at equal pressures and temperatures is:

(R₁ / R₂) = √(M₂ / M₁)

Where M₁ is the molar mass of gas 1 and M₂ is the molar mass of gas 2. R₁ is the rate of diffusion of gas 1 and R₂ is the rate of diffusion of gas 2. Hence, the rate of diffusion is inversely proportional to the molecular mass.