Chemical thermodynamic calculations were used to represent vapor-liquid equilibria and chemical equilibria for aqueous systems with HF, HNO3, and CO2-H2O-CaCO3 solutions. The entropy production related to the dissolution reaction of calcite was calculated using multiphase thermodynamics and experiments carried out in this work. Modern simulation methods combined with experiments provide a useful tool for the research and design of new processes as well as evaluating changes in the operational conditions of chemical processes. These methods are used to study metallurgical, pulp, and paper industrial processes that involve the presented aqueous solutions. (C) 2004 American Institute of Chemical Engineers.