2. As shown in the following figure, the diffusion of component A through a stagnant gas is employed to find the diffusivity of A. In this case, one boundary at the end of the diffusion path is impermeable to component B. Component A at the bottom of a cylindrical tube evaporated into the nondiffusing B. (a) By assuming that the diffusion of component A is only in z-direction, use the material balance on component A to derive the equation of continuity. (6%) (b) What is the "film theory"? (4\%) (c) By assuining that the system is at steady state and no chemical reaction, use the concept of film theory to obtain the molar flux of component A throagh the tube in terms of partial pressure and total pressure: (64) (d) Find the relation between k - and DAB in termis of the log-mean average partial pressture of component B.wherek,is the convective mass transfer coefficient (4%)