ABSTRACT: The properties of mixing, like excess free energy (Gx), excess entropy of mixing JXS (Sxs), volume of mixing (12xs) and the concentration fluctuation (Scc(0)), for He-H2, Ne-H2, and Ar-H2 mixtures have been studied as functions of composition, temperature and pressure. This is done based on statistical mechanical perturbation theory for mixtures. The short-range repulsive potential is treated as the unperturbed reference system of hard sphere mixtures. It suitably modified through a double Yukawa (DY) potential for long-range attractive potentials. A simple numerical scheme has been suggested to simulate the empirical potentials of pure elements to DY potential, which is further used to calculate the potential energy function of the binary mixtures. The constituent elements, like He, Ne and Ar, have been considered as monatomic species whereas the dimeriazation of H atoms is accounted as a hard convex body fluid. The results suggest that the segregation, hetero-coordination or both may occur in He-H2, Ne-H2 and Ar-H2 mixtures depending upon the composition, temperature and pressure conditions.