Graham’s Law of Diffusion and Effusion
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:
Effusion is the term used to describe the
passage of a gas through a tiny orifice into an evacuated chamber,
as shown in the figure below.
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.