Graham’s Law of Diffusion

A gas spreads so as to occupy any volume available to it. The spontaneous spreading of a substance throughout the given space is called Diffusion.

Diffusion can be readily observed by releasing a small quantity of L. P. G in kitchen. Its odour (smell) soon fills the whole home, because gas diffuses throughout the entire volume of home. It is found that rate of diffusion for different gases are different; the lighter gas diffuses rapidly whereas heavier gas diffuses slowly. The phenomenon of diffusion is described quantitatively by Graham’s Law which may be stated as, “Under similar conditions of temperature and pressure, the rate of diffusion of gas is inversely proportional to the square root of its density.”