Graham’s law states that the rates of effusion of two gases are inversely proportional to the square roots of their molar masses at the same temperature and pressure:
but if time is used the equation changes
Graham's Law deals with the effusion of gases. This is not to be confused with diffusion which declares that molecules will move from a place of higher concentration to a place of lower concentration. The principle of effusion depends upon a movement or diffusion of gases but it relates to the rate of travel of a gas through a predefined pathway and how the rate depends upon the molecular mass of the gas. Specifically, the law states that the relative rates of effusion of two gases through a tube or pathway of equal size is inversely proportional to the square root of the molecular masses of the gases.
The rate of effusion measures the speed at which the gas travels through the tiny hole into a vacuum. Another term to remember for the test is diffusion. Diffusion is the term used to describe the spread of a gas throughout a space or throughout a second substance.