QUESTION $4$

Assume that a solute has a $D_d$ of $2\mathrm{.}03{10}^{-9}\frac{m^2}{s}$ and that $$ is equal to $0\mathrm{.}5.$ If landfill leachate with a chloride concentration is$.$next to a clay liner that is $2m$ thick and the concentration of chloride is $2315m\frac{g}{L},$ what would be the chloride concertation at the outside of the liner after. $50$ years of diffusion. Ignore any effects of advection.