Thermodynamic Properties of Aqueous Systems

Section 5 Thermochemistry, Electrochemistry, and Kinetics CODATA Key Values for Thermodynamics Standard Thermodynamic Properties of Chemical Substances Thermodynamic Properties as a Function of Temperature Thermodynamic Properties of Aqueous Systems Heat of Combustion Electrical Conductivity of Water... 

Thermodynamic Properties as a Function of Temperature, 5-43 to 65 Thermodynamic Properties of Air, 6-1 to 3 Thermodynamic Properties of Aqueous Systems, 5-66 to 69 Thermodynamic Quantities for the... 

Fig. 2.37. Phase diagram for Ca0-Na20 Si02-(Al203)-H20 system in equilibrium with quartz at 400°C and 400 bars. Plagioclase solid solution can be represented by the albite and anorthite fields, whereas epidote is represented by clinozoisite. Note that the clinozoisite field is adjacent to the anorthite field, suggesting that fluids with high Ca/(H+) might equilibrate with excess anorthite by replacing it with epidote. The location of the albite-anorthite-epidote equilibrium point is a function of epidote and plagioclase composition and depends on the model used for calculation of the thermodynamic properties of aqueous cations (Berndt et al., 1989).

P. Duby, The Thermodynamic Properties of Aqueous Inorganic Copper Systems, Int. Copper Res. Assoc., p. 56,1977. 

Thermodynamic Properties of Aqueous Organic Systems" Engineering Sciences Data Unit, Ltd., London, 1978-79. 

Duby, P. "The Thermodynamic Properties of Aqueous Inorganic Copper Systems", International Copper Research Association New York, 1977. 

The thermodynamic treatment of systems in which at least one component is an electrolyte needs special comment. Such systems present the first case where we must choose between treating the system in terms of components or in terms of species. No decision can be based on thermodynamics alone. If we choose to work in terms of components, any effect of the presence of new species that are different from the components, would appear in the excess chemical potentials. No error would be involved, and the thermodynamic properties of the system expressed in terms of the excess chemical potentials and based on the components would be valid. It is only when we wish to explain the observed behavior of a system, to treat the system on the basis of some theoretical concept or, possibly, to obtain additional information concerning the molecular properties of the system, that we turn to the concept of species. For example, we can study the equilibrium between a dilute aqueous solution of sodium chloride and ice in terms of the components water and sodium chloride. However, we know that the observed effect of the lowering of the freezing point of water is approximately twice that expected for a nondissociable solute. This effect is explained in terms of the ionization. In any given case the choice of the species is dictated largely by our knowledge of the system obtained outside of the field of thermodynamics and, indeed, may be quite arbitrary. 

The semigrand partition function F corresponds with a system of enzyme-catalyzed reactions in contact with a reservoir of hydrogen ions at a specified pH. The semigrand partition function can be written for an aqueous solution of a biochemical reactant at specified pH or a system involving many biochemical reations. The other thermodynamic properties of the system can be calculated from F. 

A challenging subject in physical organic chemistry is the interpretation of changes in activation parameters for a given reaction as an organic co-solvent is added to the reaction in water. In order to understand these systems, we start by examining some thermodynamic properties of aqueous mixtures. These provide a convenient basis for classification of diverse systems. 

Pokrovskii V. A. and Helgeson H. C. (1995) Thermodynamic properties of aqueous species and the solubilities of minerals at high pressures and temperatures the system AI2O3-HsO-NaCl. Am. J. Sci 295, 1255-1342. 

Pemberton, R. C. Thermodynamic properties of aqueous nonelectrolytes mixtures. Vapor pressures for the system water -I- ethanol 303.15— 363.15 K determined by an accurate static method. Conf. Int. Thermodyn. Chim. Montpellier 1975, 6, 137-144. 

Figure 12.18 Eh-pH diagram for aqueous species in the system S-02-H20 at 25°C neglecting sulfate, bisulfate, and elemental sulfur showing significant stability fields for sulfite and bisulfite, thiosulfate and its conjugate acid, and tetrathionate. Reprinted from Geochim. et Cosmochim. Acta, 56, M. A. Williamson and J. D. Rimstidt, Correlation between structure and thermodynamic properties of aqueous sulfur species, 3867-80, 1992, with permission from Elsevier Science Ltd., The Boulevard, Langford Lane, Kidlington 0X5 1GB, U.K.

Duby, P. 1977. The thermodynamic properties of aqueous inorganic copper systems. In The metallurgy of copper. INCRA Monograph IV. 

Extensions beyond the data base of (2) are largely untested and include additions to PITZER.DATA for (1) the calculation of the thermodynamic properties of aqueous solutions containing Fe(II), Mn(II), Sr +, Ba2+, Li+, and Br (2) the estimation of the temperature dependence of many of the single-salt parameters from selected literature data and (3) the calculation of the thermodynamic properties of NaCl solutions to approximately 300 °C along the vapor pressure curve of water beyond 100 C (18)-Except for the NaCl-H20 system, the PHRQPITZ aqueous model should not be used outside the temperature range 0 to 60 C. Several recent evaluations of the temperature dependence of Pitzer interaction parameters to relatively high temperatures (19-21) have not yet been incorporated in the PHRQPITZ data base. 

The study of thermodynamic properties of aqueous solutions of inert gases was the subject of my PhD thesis. In the early 1960s, not much was known about these systems. Experimental data were very scarce and inaccurate. Theory was highly speculative. Nevertheless, I chose this subject mainly for one reason I was fascinated by the hearsay that inert solute dissolved in water lowers the entropy of the system. Lowering the entropy meant increasing the structure of water. But why How can inert solutes cause an increase in structure and lower the entropy That was quite a mystery. I say it was hearsay because the experimental data on solubilities of inert solutes was very inaccurate. The entropy of solution was determined from the temperature dependence of the solubility. That renders the uncertainty of the values of the entropy of solution even larger than the uncertainty of the solubilities themselves. At that time I was not aware of the fact that the so-called standard entropy of solution was itself an uncertain measure of the entropy of solvation. 

Friedman s model fits the thermodynamic excess functions (osmotic coefficient, excess volume, and excess energy) of aqueous solutions of alkali and earth alkaline halides up to l-M ionic strength and of tetraalkylammo-nium halides up to 0.4 M. The variation of the A/y parameters with the ionic parameters is chemically meaningful and permits the estimation of thermodynamic properties of unknown systems by the combination of the parameters known from appropriate other systems. 

The two-term crossover Landau model has been successfully applied to the description of the near-critical thermodynamic properties of various systems, that are physically very different the 3-dimensional lattice gas (Ising model) [25], one-component fluids near the vapor-liquid critical point [3, 20], binary liquid mixtures near the consolute point [20, 26], aqueous and nonaqueous ionic solutions [20, 27, 28], and polymer solutions [24]. 

This 268 page article is concerned with the prediction of the thermodynamic properties of aqueous electrolyte solutions at high temperatures and pressures. There is an extensive discussion of the fundamental thermodynamics of. solutions and a discussion of theoretical concepts and models which have been used to describe electrolyte solutions. There is a very extensive bibliography ( 600 citations) which contains valuable references to specific systems of interest. Some specific tables of interest to this bibliography contain Debye-Hiickel parameters at 25 C, standard state partial molar entropies and heat capacities at 25 °C, and parameters for calculating activity coefficients, osmotic coefficients, relative apparent and partial molar enthalpies, heat capacities, and volumes at 25 °C. 

International Data Series B. Thermodynamic Properties of Aqueous Organic Systems... 

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