Enthalpy, h (kcal/kg) 700 600 500 400 300 200 98°C 46 urva conjuga Congruent curve ethanol/water (101.3 kPa) Vapor saturated 95°C 92°C 100 Liquid saturated 90% 88°C 85°C 82°C 40°C Liquid 20°C Linh Solidification line 80°C 3.64 78°C Solid -100 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Fr Mass fraction of ethanol ol 77.65°C 1.0

Using the enthalpy-composition diagram for the ethanol/water mixture at 1 atm, determine:

a) The composition of the first vapor bubble resulting from heating a liquid with 70% (by mass) ethanol, initially at 40ºC.

b) The energy required to vaporize 60% of a mixture initially at 80ºC and containing 40% ethanol.

c) The compositions of the liquid and vapor in equilibrium under the conditions from the previous item.