(Solved): A polymer solid is saturated with a salt solution such that the initial concentration of salt is co ...

A polymer solid is saturated with a salt solution such that the initial concentration of salt is constant and equal to \( 0.1 \mathrm{kmol} \mathrm{m}^{3} \). The solid is in the shape of a cube, \( 10 \mathrm{~cm} \) on a side. The diffusion coefficient of salt in the polymer is equal to \( 2.0 \times 10^{-10} \mathrm{~m}^{2} / \mathrm{s} \). At zero time, four sides of the cube are washed with pure water of sufficient velocity that the convective mass transfer coefficient may be assumed infinite. The two sides not contacted with water are kept dry, these sides are located at the planes \( z=0 \) and \( z=10 \). I. Find the time in hours for the concentration in the middle of the solid to drop to \( 10 \% \) of the original concentration. 2. If all sides of the polymer solid are placed in contact with pure water, what is the concentration in the middle of the solid after 5 months of continuous washing? Note: You need to show the condition of the polymer solid on the chart provided below.