Graham s Law of Diffusion

Graham s law : Graham s law, also known as Graham s law of effusion, was formulated by Scottish physical chemist Thomas Graham in 1848. Graham found experimentally that the rate of effusion of a gas is inversely proportional to the square root of the mass of its particles.
1- Graham s Law of Diffusion
The rate at which gases diffuse is inversely proportional to the square root of their densities.
Since volumes of different gases contain the same number of particles , the number of moles per liter at a given T and P is constant. Therefore, the density of a gas is directly proportional to its molar mass (MM).when a volume of gas is opened to another volume with less pressure, the gas can either diffuse or effuse into the container. The main difference between diffusion and effusion is the barrier between the two volumes. Effusion : When there is a barrier with one or many small holes that prevent the gas to expand into the new volume unless a gas molecule happens to travel through the hole. The term "small" when referring to the holes are holes with diameters less than the mean free path of the gas molecules. The mean free path is the average distance traveled by an individual gas molecule before it collides with another gas molecule. Diffusion: occurs when the holes in the barrier are larger than the mean free path of the gas. If there is no barrier at all, you can think of a barrier with one large hole big enough to cover the boundary between the two volumes. This would mean the gas will diffuse into the new container.
This diagram shows effusion (left) and diffusion (right). Effusion occurs through a hole smaller than the mean path of moving particles while diffusion occurs through a hole large enough allow multiple particles to pass at once.