Hydrogen can be separated from a natural gas by diusion through a round tube. The rate of separation is given by$,$

$N=2DpR$

Whete,

$N=$ the rate of transport of $H_2$ from the tube, gmoles $/($sec$)($cm of length of the tube$)$

$D=$ diffusion coefficient

$P=$ molar density of $H_2,$ gmoles $/1c{m}^3$

$R=log$ mean radius of the tube, $(r_2-r_1)/$

$In(\frac{r_2}{r_1}),$ with $r$ in $cm.$

What are the units of D$?(15$marks$)$