Example 2: In a rectification column, toluene is diffusing from gas to liquid and benzene from liquid to gas at 30C and 101.3 kPa pressure under conditions of equal molar counter diffusion. At one point in the column, the molar concentrations of toluene on the two sides of a gas film 0.5 mm thick are 70% and 20%, respectively. Assuming the diffusivity of benzene toluene vapor under the operating conditions to be 0.38 x 10-5 m/s, estimate the rate of diffusion of toluene and benzene in kg/hr across an area of 0.01 m