Aqueous species, thermodynamic properties

Thermodynamic. Thermodynamic properties of Pu metal, gaseous species, and the aqueous ions at 298 K are given in Table 8. Thermodynamic properties of elemental Pu (44), of alloys (68), and of the gaseous ions Pu", PuO", PuO" 27 PuO 2 (67) have been reviewed, as have those of aqueous ions (64), oxides (69), haUdes (70), hydrides (71), and most other compounds (65). 

Johnson, J. W., E. H. Oelkers and H. C. Helgeson, 1991, Supcrt92 a software package for calculating the standard molal thermodynamic properties of minerals, gases, aqueous species, and reactions from 1 to 5000 bars and 0° to 1000 °C. Earth Sciences Department, Lawrence Livermore Laboratory. 

Other thermodynamic properties of aqueous solutions are being evaluated. A recent publication reports values calculated for the association constants of aqueous ionic species at 298 K for alkaline earth salts (Staples, 1978). 

Shock EL, Sassani DC, Willis M, Sverjensky DA (1997) Inorganic species in geologic fluids Correlations among standard molal thermodynamic properties of aqueous cations and hydroxide complexes. Geochim... 

The thermodynamic properties of snbsnrface aqneons solntions are expressed in terms of a single species solntion activity coefficient for each molecnlar constituent. Its composition, however, shonld be considered on the basis of molecnlar specia-tion in the aqueous solution, which in tnm is related to biological nptake exchange reactions and transport throngh the snbsnrface. 

Table 8.22 Partial molal thermodynamic properties of organic aqueous species at 25 HKF model, after Shock and Helgeson (1990). 

Discrete values of the HKF model parameters for various organic aqueous species are listed in table 8.22. Table 8.23 lists standard partial molal thermodynamic properties and HKF model parameters for aqueous metal complexes of monovalent organic acid ligands, after Shock and Koretsky (1995). 

Shock E. L. and Helgeson H. C. (1988). Calculations of the thermodynamic and transport properties of aqueous species at hight pressures and temperatures Correlation algorithms for ionic species and equations of state predictions to 5Kb and 1000°C. Geochim. Cosmochim. Acta, 52 2009-2036. 

In addition, data for the thermodynamic properties of the species themselves are given as mentioned above for the primary master species (of course, no aqueous activity coefficients are required for solids and gases). 

The relative positions of the H20—02 boundary and the Mn2+—Mn02 boundaries for both 10"3 and 10"7M activities of aqueous Mn2+ indicate that for pH values greater than about 4, Reaction 58 is spontaneous. Similarly, the pure solid phases MnCOa and Mn(OH)2 are unstable with respect to oxidation to MnO >. Extensive interpretations of manganese chemistry in terms of the thermodynamic properties of the oxides and on other solid phases and solution species of manganese can be found in the recent literature (3,14, 24). 

Armstrong D, Rauk A, Yu D (1992) Aminoalkyl und alkylaminium free radicals and related species structures, thermodynamic properties, reduction potentials and aqueous energies. J Am Chem Soc 115 666-673... 

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. 

In order to discuss thermodynamic properties in dilute aqueous solutions at temperatures other than 298.15 K, it is necessary to have the standard enthalpies of the species involved. Over narrow ranges of temperature, calculations can be based on the assumption that Af// values are independent of temperature, but more accurate calculations can be made when Cpm(i) values are known. It is also necessary to take into account the temperature dependencies of the numerical coefficients in equations 3.6-4 to 3.6-6. Clarke and Glew (1980) calculated the Debye-Hiickel slopes for water between 0 and 150°C. They were primarily concerned with electrostatic deviations from ideality of the solvent osmotic... 

As we have seen in the preceding chapter, the standard thermodynamic properties of species in aqueous solutions are functions of ionic strength when they have electric charges. Substituting equation 3.6-3 for species j and for H + in equation 4.4-9 yields the standard transformed Gibbs energy of formation of species j as a function of pH and ionic strength at 298.15 K ... 

Statistical mechanics provides a bridge between the properties of atoms and molecules (microscopic view) and the thermodynmamic properties of bulk matter (macroscopic view). For example, the thermodynamic properties of ideal gases can be calculated from the atomic masses and vibrational frequencies, bond distances, and the like, of molecules. This is, in general, not possible for biochemical species in aqueous solution because these systems are very complicated from a molecular point of view. Nevertheless, statistical mechanmics does consider thermodynamic systems from a very broad point of view, that is, from the point of view of partition functions. A partition function contains all the thermodynamic information on a system. There is a different partition function... 

The thermodynamics properties of an electrolytic solution are generally described by using the activities of different ionic species present in the solution. The problem of defining activities is however somewhat more complicated in electrolytic solution than in solutions of nonelectrolytes. The requirement of overall electrical neutrality in the solution prevents any increase in the charge due to negative ions. Consider the 1 1 electrolyte AB which dissociates into A+ ions and B ions in the aqueous solution. 

A new thermodynamic model for the Cu(I,II)-HC1-H20 system was developed on the basis of the representative data on GuGl(s) solubility in aqueous solutions of HC1 in a concentration interval from 1 to 6 mol kg1 HG1 (Akinfiev, 2009). The model takes into account a number of aqueous Cu(I) species [Cu+, CuOH°, Cu(OH)2, CuC1°, CuClj, HCuCL ], aqueous Cu(II) species [Cu2 CuOH+, CuO°, HCuO , CuOJ- CuCl+, CuCL , GuGlg, CuClJ)] and a mixed Cu(I)/Cu(II) chloride aqueous complex, Cu2Cl . The thermodynamic approach used a modelling approach based on i) the standard thermodynamic properties of the listed above species ii) a model for the activity coefficients iii) use of HCh software (Shvarov, 1999). 

Electrolytes pose a special problem in chemical thermodynamics because of their tendency to dissociate in water into ionic species. It proves to be less cumbersome at times to describe an electrolyte solution in thermodynamic-like terms if dissociation into ions is explicitly taken into account. The properties of ionic species in an aqueous solution cannot be thermodynamic properties because ionic species are strictly molecular concepts. Therefore the introduction of ionic components into the description of a solution is an etfrathermodynamic innovation that must be treated with care to avoid errors and inconsistencies in formal manipulations.20 By convention, the Standard State of an ionic solute is that of the solute at unit molality in a solution (at a designated temperature and pressure) in which no interionic forces are operative. This convention implies that an electrolyte solution in its Standard State is an ideal solution,21 as mentioned in Section 1.2. 

Standard-State chemical potentials for aqueous and solid A1(III) species are discussed carefiilly in the context of dissolution-precipitation reactions by B. S. Hemingway, R. A. Robie, and J. A. Apps, Revised values for the thermodynamic properties of boehmite, A10(OH), and related species and phases in the system Al-H-O, Am. Mineralog. 76 445 (1991). 

The two primary reference works on inorganic thermochemistry in aqueous solution are the National Bureau of Standards tables (323) and Bard, Parsons, and Jordan s revision (30) (referred to herein as Standard Potentials) of Latimer s Oxidation Potentials (195). These two works have rather little to say about free radicals. Most inorganic free radicals are transient species in aqueous solution. Assignment of thermodynamic properties to these species requires, nevertheless, that they have sufficient lifetimes to be vibrationally at equilibrium with the solvent. Such equilibration occurs rapidly enough that, on the time scale at which these species are usually observed (nanoseconds to milliseconds), it is appropriate to discuss their thermodynamics. The field is still in its infancy of the various thermodynamic parameters, experiments have primarily yielded free energies and reduction potentials. Enthalpies, entropies, molar volumes, and their derivative functions are available if at all in only a very small subset. 

A further advantage of an SCM approach is that thermodynamic parameters for adsorption reactions can be compared with the thermodynamic properties of other types of reactions, to assess correlative relations that may be used to predict the behaviour of chemical species for which experimental data are currently lacking. In Fein et al. (1997) the authors compared model results for equilibrium constants of metal-bacteria adsorption reactions, and found a strong correlative relationship between these values and corresponding equilibrium constants for metal-oxalate and metal-tiron (4,5-dihydroxy-m-benzenedisulphonic acid) aqueous... 

Shock, E. L., Oelkers, E. H., Johnson, J. W., Sveijensky, D. A. Helgeson, H.C. (1992). Calculation of the thermodynamic behavior of aqueous species at high pressures and temperatures effective electrostatic radii, dissociation constants, and standard partial molal properties to 1000 °C and 5 kb. Journal of the Chemical Society (London) Faraday Transactions, 88, 803—26. 

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