This work develops a thermodynamic model for ionic speciation and volumetric properties of the ternary system CuCl2-HCl-H2O from 273.15 to 373.15 K and at 101.3 kPa, a system relevant to chalcopyrite leaching in chloride media and hydrogen production via the copper-chlorine thermochemical cycle. The Pitzer equations were used to estimate water activities, CuCl2 & sdot;2H2O(cr) solubilities, and densities, calibrated using published experimental data. The speciation model includes Cu2+, H+, CuCl+, Cl-, CuCl02, and HCl0, showing reasonable species distribution results as a function of temperature and total concentration. Based on volume of mixing calculations at 298.15 K, CuCl2 acts as a structure breaker of water, while HCl behaves as a structure maker. New Pitzer parameters and the solubility product constant of CuCl2 & sdot;2H2O(cr) are provided as temperature-dependent functions. The model demonstrates high accuracy in reproducing experimental data and offers insights into the physicochemical behavior of concentrated CuCl2 + HCl + H2O solutions.