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QUESTION 4 (15 MARKS) An open cylindrical tank is filled with pure ethanol and the liquid level is 0.3 m from the top as shown in Figure 4. Ethanol diffuses through the stagnant air film above the liquid ethanol. The mole fraction of ethanol in the air adjacent the surface of the liquid ethanol (YN) in the tank is 0.1. The circulation of the air immediately above the tank is adequate to assume negligible concentration of ethanol at the top of the tank. The tank and air space are at 25C and 101.3 kPa. The diffusivity of ethanol is 1.33x10-5 m/s under this condition. Calculate the rate of ethanol evaporation from the tank at steady state in kg/s. Molecular weight of ethanol = 46 kg/kmol. (15 marks) YA YA 0.3 m Ethanol 2 m