a) Show that for equi-molar counter diffusion from a sphere to a surrounding static infinite medium, the Sherwood number Ked/D.a) based on the diameter of the sphere is equal to 2. Where Ks is the mass transfer coefficient, dis te duameter of tie sphere and Das is the molecular diffusivity. b) A small quantity of gas "A" can diffuse through a solid wall of state of legs 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 grove the rate of mass transfer of this gas is given by this equation 21L DesCase -CO WA= aca + ) aca + 1 1ONAL, ONA: + r de =RA =Dia ot Org