How much heat is required to convert 27.0 g of ethanol at 23 C to the vapor phase at 78 C in kJ? Ethanol (C2H5OH) boils at 78 C. Its density is 0.789 g/mL. The enthalpy of vaporization is 38.56 kJ/mol. The specific heat of liquid ethanol is 2.3 J/g-K.