a) Show that for equi-molar counter diffusion from a spirere to a surrounding stationary infinite medium, the Sherwood number (Ky d/Daa) based on the diameter of the sphere is equal to 2. Where Ks is the mass transfer coefficient. d is the diameter of tie sphere and Das is the molecular diffusivity. b) A small quantity of gas "A" can diffuse through a solid wall of a sabe of lengi in which it flows in only r-direction at a steady-state without a chemical reaction. Use the general flux equation and the general mass balance equation of mass transfer to prove the rate of mass transfer of this gas is given by this equation 21L Dea Ce-Co) WA= RO USA - (NA) + I NA ONA + de =RA Cus achatin cal