A laboratory apparatus to measure the diffusion coefficient of vapor-gas mixtures consists of a vertical, small-diameter column containing the liquid phase that evaporates into the gas flowing over the mouth of the column. The gas flow rate is sufficient to maintain a negligible vapor concentration at the exit plane. The column is 150 mm from the liquid interface to the top, and the pressure and temperature in the chamber are maintained at 0.25 atm and 320 K, respectively. For calibration purposes, you've been asked to calculate the expected evaporation rate (kg/h-m for a test with water and air under the foregoing conditions, using the known value of D for the vapor-air mixture