$1-2.$ Hydrogen at $1\mathrm{.}0$ MPa is to be stored at $400C$ in outer space, in a thin walled $(0\mathrm{.}1mm)$ spherical iron tank of $0\mathrm{.}1$ m radius. You are to calculate the rate of pressure drop $(MP\frac{a}{s})$ as a result of diffusion of hydrogen through the wall.

Take $D={10}^{-8}\frac{m^2}{s},$ and assume that the concentration of hydrogen in the iron at either side of the wall is the equilibrium solubility given by the equation

$C(P)={10}^{-5}(P{)}^{\frac{1}{2}}gm\frac{H}{g}$mFe,$(Pin$ MPa $).$

$J$~$=-D\frac{c}{r},{}_{Fe}=7\mathrm{.}874g*c{m}^{-3}$

$50$