1. Show for a 1 st order reaction in a porous cylindrical catalyst pellet (length>>diameter), with no volume change and negligible heat of reaction, that the mass balance on a differential element gives dC 1 dC (26) + dr r dr R Where C=concentration of reactant at radius r r=radial position R=pellet radius O2 R2/4 (kcat/Deff)=(Thiele Modulus) k=reaction rate constant/unit area s=surface area/unit volume Deff effective diffusivity C