Thomas Graham found that, at a constant temperature and pressure the rates of effusion of various gases are inversely proportional to the square root of their masses.
∨ ∝ 1/√M.
Where, ∨ is the rate of diffusion.
M is the molar mass of the gas.
For Ne and Kr:
(∨)Ne/(∨)Kr = √(M of Kr/M of Ne) = √(83.8 / 20.2) = 2.037.
