Porous silica gel is used to adsorb propane from helium at \(373 \mathrm{~K}\) and \(1 \mathrm{~atm}\). Typical values of parameters for porous silica gel are as follows: porosity \(=0.486\), tortuosity \(=3.35\), and pore diameter =22 Å.

(a) Calculate the Knudsen number for diffusion inside the pores.

(b) Calculate the effective diffusivity of propane under these conditions.