4 Derive the expression for the molar flux through a non-uniform cross section shown below. In the above figure, z is the linear coordinate along the length; r1 and r2 are the radii at sections 1 and 2 respectively. Assume, in a mixture of A and B at a total pressure P and temperature T, component A is transferred through stagnant non-diffusing B from section 1 to section 2 . The corresponding partial pressure of A at 1 and 2 are PAl and PA2 respectively. 5 In the process of determining the diffusion coefficient of an organic liquid that has a density of 790kg/m3 and a molar mass of 58g/mol Winklemann experiment wis performed (at 290K and 99.75kPa ) using air as the flowing stream. The liquid level in the tube initially was 18 mm from the top and the level falls to 27.5mm in 15,000 seconds. If the vapor pressure of the organic liquid is 21.95kPa, calculate its diffusivity in air at experimental condition