Consider unsteady diffusion across a membrane of thickness L. Initially, the concentration of solute in the membrane is zero. At time zero, the concentration at x=0 is raised to C0 and the concentration at x=L is maintained at zero.
(1) Write the Ficks second law applied to this problem (including initial and boundary conditions).
(2) Under what condition can you use the semi-infinite medium assumption to solve this diffusion problem?