The enthalpy of vaporization is the amount of heat that must be added to a liquid substance to transform it into a gas. Dipole-Dipole interactions are intermolecular force of attraction between polar molecules. Stronger the dipole-dipole interactions, higher will be the heat energy required to break these interactions and vaporize the liejuid. Since, the liquids A,B and C have molar enthalpy of vaporization as 23.3,4! and 29‌kJ mol , the order of dipole-dipole attractive interactions will be B>C>A.
