P4. (8 pts) Water and ethanol are flash distilled in a cascade of three drums connected as shown below, each operating at 1 atm. Use the attached figure for XY data. The feed is 60 mol% ethanol. One-third of the feed is vaporized in the first drum, two-thirds of the feed to the second drum is vaporized, and one- half the feed to the third drum is vaporized. (a) What are the compositions of streams L3 and V3? Plot operating lines that describe each drum on the X-Y diagram. (b) The liquid streams L and L must be heated and pressurized so that they can be flashed again. How much enthalpy must be added to stream L (per kilogram of stream L) prior to flashing in drum three to achieve the separation described? (Use Figures 2-3 and 2-4 from the text and mind your units.) Vapor mole fraction EtOH 0.3 0.4 0.5 44 2 913 928 L 0 F Ethanol-water X-Y diagram: 1 0.1 0.2 V L 1.0 atm 3 0.3 0.4 0.5 0.6 Liquid mole fraction EtOH V3 L3 0.7 0.8 0.9