For the conditions of Exercise 15.16, estimate the effective diffusivity of benzene vapor in the pores of silica gel with the following properties: particle density = 1.15 g/cm³ particle porosity = 0.48, average pore diameter = 30 A, and tortuosity = 3.2. Consider all mechanisms of diffusion. The adsorption equilibrium constant is given in Example 15.11, and the differential heat of adsorption is – 11,000 cal/mol.