Answer: -
H₂ will diffuse the fastest.
Explanation: -
According to Graham's Law of Diffusion
The rate of diffusion is inversely proportional to the square root of it's density or molar mass. So the lower the molar mass faster the rate of diffusion.
Molar mass of Ne = 20 g / mol
Molar mass of CH₄ = 12 x 1 + 1 x 4 = 16 g /mol
Molar mass of Ar = 40g / mol
Molar mass of H₂ = 1 x 2 = 2 g / mol
Thus H₂ will diffuse the fastest.
