Compare estimates of the diffusion coefficient of an ethanol-water mixture at $10^\circ\mathrm{C}$ (283 K), under conditions that (1) ethanol is the solute and water is the solvent and (2) water is the solute and ethanol is the solvent. Ethanol has the molecular formula C$_2$H$_5$OH and a molecular weight of 46 g/gmole, and water (H$_2$O) has a molecular weight of 18 g/gmole. At $10^\circ\mathrm{C}$, the liquid viscosity of water is $1.306 \times 10^{-3}$ Pa s (1.306 cP), and the liquid viscosity of ethanol is $1.394 \times 10^{-3}$ Pa s (1.394 cP). The molecular volume of water is $18.9\ \mathrm{cm^3/gmole}$ and the molar volume of ethanol (EtOH) $59.2\ \mathrm{cm^3/gmole}$. The association parameter of the solvent $\Phi_{water} = 2.6$ and $\Phi_{EtOH} = 1.5$.

In a rectification column, toluene is diffusing from gas to liquid and benzene from liquid to gas at temperature of $30^\circ\mathrm{C}$ and pressure $101.3\ \mathrm{kN/m^2}$ under conditions of equal molar counter diffusion. At one point in the column, the molal 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 vapour under the operating conditions to be $0.38 \times 10^{-5}\ \mathrm{m^2/s}$, estimate the rate of diffusion of toluene and benzene in kg/hr across an area of $0.01\ \mathrm{m^2}$. The molecular weights of toluene and benzene are 92 and 78 g/mol, respectively. The ideal gas constant is equal to $8.314\ \mathrm{m^3\,Pa\,K^{-1}\,mol^{-1}}$.