Gibbs energy approach for aqueous processes with HF, HNO3, and CO2 ? CaCO3
Chemical thermodynamic calculations were used to represent vapor–liquid equilibria and chemical equilibria for aqueous systems with HF, HNO3, and CO2H2OCaCO3 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. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1942–1947, 2004
Estimation of Pitzer's ion interaction parameters for electrolytes involved in complex formation using a chemical equilibrium model
Pitzer's ion interaction model has been widely accepted for calculating the thermodynamic properties for electrolytes at high ionic strength. For weak electrolytes, a better estimation can be obtained by combining the model with chemical equilibria. The method of calculation is to treat each individual species as a single, separated ion. The concentration of each ion will be constrained by the mass balance equation and its activity will be guarded by the stability constants. Including chemical equilibria in Pitzer's model provides not only a better estimation of the thermodynamic properties of weak electrolytes but also a better understanding of the equilibrium among the complexes. The results may be used for correcting the effect from high ionic strength solution when determining the stability constants. When considering chemical equilibria, some of the parameters reported by Pitzer may have to be reestimated. The method of estimation and comparison between final results are presented. The binary system of HF, and the ternary systems of CuCl2 in NaCl and in HCl are used for demonstration.
Thermodynamics of electrolytes. 7. Sulfuric acid
Although the thermodynamic properties of sulfuric acid above 0.1 M and near 25/sup 0/C are well established numerically, they have not been represented accurately by equations which are based upon the ionic species present, H/sup +/, HSO/sub 4//sup -/, and SO/sub 4//sup 2 -/. We have developed and fitted such equations over the range from 0 to 6 M in a system compatible with those for fully dissociated, strong electrolytes. The enthalpy is treated as well as the activity and osmotic coefficients. These equations also establish the solute standard state and the relationship between the properties of sulfuric acid in that state with those for the pure acid. Among the results obtained (for 25/sup 0/C) are the dissociation constant 0.0105 and the heat of dissociation -5.61 kcal mol/sup -1/ for HSO/sub 4//sup -/ and the entropy of SO/sub 4//sup 2 -/, 4.2 +- 0.2, and of HSO/sub 4//sup -/, 32.1 +- 0.3 cal K/sup -1/ mol/sup -1/. Also for the reaction H/sub 2/SO/sub 4/(l) = 2H/sup +/(aq) + SO/sub 4//sup 2 -/(aq), ..delta..H/sup 0/ = -22844, ..delta..G/sup 0/ = -12871 cal mol/sup -1/.