An aqueous solution of urea (viscosity-1 cp, density-1 g/ml) is to be passed through a membrane composed of non-uniform, circular pores with straight channels. some preliminary experiments have shown that the pore diameters dp range from 20 microns to 40 microns in size, following the probability distribution p(p)/94 (dp in units of microns). urea has a molecular diameter of 5.28 angstroms, with a diffusion coefficient of 138x10-6 cm2ls. given that the membrane is 5.5 microns thick, with 300 pores per mm2 membrane surface area, determine: (a) the pressure difference (in atm) across the membrane in order to drive the solution through the (b) does the required pressure difference increase or decrease if a tortuous membrane geometry is used? membrane at 36 g/cm*-hr (hint: you may use the average pore diameter in your calculations). explain. you realize that the results from the preliminary experiments were reported with the wrong units, and the pore diameters actually range from 20-40 angstroms in size, following the same probability distribution p(dp) e-/94 (where dp is in units of angstroms). given that the membrane is 5.5 angstroms thick, determine: (c) the number of pores per membrane surface area required to maintain the same porosity as determined in part (a) (d) the molar concentration gradient required in order to drive urea through the membrane at 36 g/cm-hr?