Problem 3. Rate of leaching In studying the rate of leaching of a substance from solid particles by a solvent B, we may postulate that the rate-controlling step is the diffusion of from the particle surface through a stagnant liquid film thickness out into the main stream. The molar solubility of in B is CA0 and the concentration in the main stream is CA. See Figure 1 for the schematic. 1. Obtain a differential equation for CA as a function of z by making a mass balance on over a thin slab of thickness z. ssume that D is constant and that is only slightly soluble in B. Neglect the curvature of the particle. 2. Show that, in the absence of chemical reaction in the liquid phase, the concentration profile is linear. 3. Show that the rate of leaching per unit area is given by, N,z=D(CA0CA)/