4. What is the rate of the following reaction (based on unit surface area of the catalyst) occurring on a flat catalyst surface at a temperature T and a total pressure P: Decomposition reaction of the type 2A 3B It is assumed that (a) the reactions are all diffusion-controlled, i.e. the concentration of A at the catalyst surface is negligibly small, (b) the diffusion of the gases occurs through a stagnant gas-film of thickness , and (c) the partial pressure of B in the bulk gas is Pbo