State and explain Graham's law of Diffusion.

Explanation

Graham.s law of diffusion : At a given temperature and pressure, the rate of diffusion of a gas.is inversely proportional to the square root of density, vapour density or molecular weight.
` r prop (1)/( sqrt(d)), r prop (1)/( sqrt((VD))),r prop (1)/( sqrt((M ))`
If `r_1` and `r_2` are the rates of diffusion of two gases d, and d, are their densities respectively, then
` (r_1)/(r_2) = sqrt((d_2)/(d_1))`
This equation can be written as:
` (r_1)/(r_2) = sqrt((d_2)/(d_1)) = sqrt((VD_2)/(VD_1)) = sqrt((M_2)/(M_1))`
Comparison of the volumes of the gases that diffuse in the same time. Let `V_1`, and `V_2`, are the volumes of two gases that diffuse in the same time t.
` (r_1)/(r_2) = ((V_1)/(t_1))/((V_2)/(t_2)) `
When time of flow is same then: ` (r_1)/(r_2) = (V_1)/(V_2)`
When volume is the same then :` (r_1)/(r_2) = (t_2)/(t_1)`
Applications:
` to ` This principle is used in the separation of isotopes like `U^(235) and U^(238)`
` to ` Molar mass of unknown gas can be determined by comparing the rate of diffusion of a known gas molecular mass.
` to` Ansil.s alarms which are used in coal mines to detect the explosive marsh gas works on the principle of diffusion.