Recently, excess enthalpies of polar-nonpolar liquid mixtures were measured and discussed qualitatively in our laboratory. In order to discuss the thermochemical behaviors of their solutions quantitatively, the free volume theory was extended to the polar-nonpolar liquid mixture using the so-called Scott's two fluid model. The resulting expression for excess enthalpy consists of three contributions of dispersion, dipole-dipole and dipole-induced dipole interactions. It was compared with the experimental excess enthalpies for CCl₄-cis-dichloroethylene, dichloroethylene isomers mixtures, and chlorobenzene, o- and m- dichlorobenzene-cyclohexane and-benzene systems. It was found that the molecular orientation in solution was predicted from an adjustable parameter m.