Question
Longest mean free path stands for :
A.
$${H_2}$$
B.
$${N_2}$$
C.
$${O_2}$$
D.
$$C{1_2}$$
Answer :
$${H_2}$$
Solution :
$$\eqalign{
& {\text{The mean free path,}} \cr
& \lambda = \frac{1}{{\sqrt 2 \pi {a^2}N}} \cr
& {\text{or}}\,\lambda \alpha \frac{1}{{{a^2}}},\,{\text{where}}\,a = {\text{molecular}}\,{\text{diameter}} \cr
& \therefore \,\,\,{\text{Smaller the molecular diameter, longer the mean free}} \cr
& {\text{path}}{\text{. Hence}}\,{H_2}\,{\text{is}}\,{\text{the}}\,{\text{answer}}{\text{.}} \cr} $$