6.7 Graham’s Law of Diffusion
The phenomenon of diffusion of a gas can be defined as the tendency of a gas to spread uniformly throughout the space available to it.
The relation between its density and the rate of diffusion of a gas can be represented by Graham’s law which states that "The rate of diffusion of a gas is inversely proportional to the square root of its density under given conditions of temperature and pressure."
It can be mathematically expressed as
If r_{1} & r_{2 }are rates of diffusion with densities d_{1 }& d_{2} the above equation becomes,
Vapor density of a gas can be calculated if 0.08 dm^{3} of gas diffuses in the same time as 0.002 dm3 of chlorine having vapor density 35.5.
r_{1 }= rate of diffusion of gas = 0.08 dm^{3}/t
r_{2} = rate of diffusion of chlorine = 0.002 dm^{3}/t
D_{1} = ?
D_{2} = 35.5
