From a certain apparatus, the diffusion rate of hydrogen has an average value of `28.7 cm^(3) s^(-1)`. The diffusion of another gas under the same conditions is measured to have an average rate of `7.2 cm^(3) s^(-1)`. Identify the gas. [Hint : Use Graham's law of diffusion: `R_(1)//R_(2) = (M_(2) //M_(1) )^(1//2)`, where `R_(1), R_(2)`, are diffusion rates of gases 1 and 2, and `M_(1)` and `M_(2)` their respective molecular masses. The law is a simple consequence of kinetic theory.]
