Briefly explain the difference between mass transfer coefficient and diffusion coefficient using a suitable diagram (only a brief sketch) of the diffusion layer model for a reaction between aqueous species and a solid (see lecture slides/recordings). (b) Assume that the mass transfer of A controls the rate of reaction between A and B at each of the three interphases (i), (ii) and (iii) shown below. Comment with reasons (one sentence only in each case) regarding the phase through which the transfer of A will control the reaction rate (solid, gas or aqueous).

(ii)