# Graham's Law Of Diffusion/Effusion

## Graham's Law Of Diffusion/Effusion

The ability of a gas to spread and occupy the whole available volume irrespective of other gases present in the container is called diffusion.

Effusion is the process by which a gas escapes from one chamber of a vessel through a small opening or an orifice. Thomas Graham in 1831 proposed the law of gaseous diffusion. The law states under similar conditions of temperature and pressure, the rates of diffusion of gases are inversely proportional to the square roots of their densities. where is the rate of diffusion and d is the density of the gas.

Now, if there are two gases A and B having r1 and r2 as their rates of diffusion and d1 and d2 their densities respectively. Then Here M1 and M2 are the molecular masses of the gases having densities d1 and d2 respectively.

Graham’s law of diffusion also holds good for effusion.

### Effect of pressure on state of diffusion

The rate of diffusion (r) of a gas at constant temperature is directly preoperational to its pressure 