In this study, a predictive model is presented for estimation of second order thermodynamic properties of electrolyte solutions. In order to provide a comprehensive understanding, the capability of modified electrolyte PC-SAFT up to high pressure and temperature has been studied. In addition to the first order derivative thermodynamic properties, the Gibbs free energy, enthalpy and heat capacity of aqueous electrolyte solutions at infinite dilution are predicted. Using new methodology, the dielectric constant is modified to keep the pressure, temperature, and ionic strength dependency. Our results show that the Born term has a significant contribution on prediction of second order derivative properties. Meanwhile the impact of temperature-dependent solution dielectric constant on standard state heat capacity is studied. Finally, the isobaric heat capacity at various salt concentrations is predicted without any adjustable parameters. The results of this work indicate an acceptable agreement with experimental data especially at high pressure and temperature. (C) 2017 American Institute of Chemical Engineers