Graham's law of diffusion was formulated by Scottish physical chemist Thomas Graham in 1848. Graham found experimentally that the rate of diffusion of a gas is inversely proportional to the square root of the mass of its molecular mass. This formula can be written as:
Rate1Rate2=√M2M1
Here, Rate1 is the rate of diffusion of the first gas (volume or number of moles per unit time).
Rate2 is the rate of diffusion of the second gas.
M1 is the molar mass of gas 1.
M2 is the molar mass of gas 2.