The mass diffusivity of ethanol (ρ = 789 kg/m3 and M = 46 kg/kmol) through air was determi...

The mass diffusivity of ethanol (ρ = 789 kg/m3 and M = 46 kg/kmol) through air was determined in a Stefan tube. The tube has a uniform cross-sectional area of 0.8 cm2. Initially, the ethanol surface was 10 cm from the top of the tube; and after 10 hours have elapsed, the ethanol surface was 25 cm from the top of the tube, which corresponds to 0.0445 cm3 of ethanol being evaporated. The ethanol vapor pressure is 0.0684 atm, and the concentration of ethanol is zero at the top of the tube. If the entire process was operated at 24°C and 1 atm, determine the mass diffusivity of ethanol in air. Answer: 1.37 × 10 5 m2/s