Thermodynamic Properties of Aqueous Ions

This table contains standard state thermodynamic properties of positive and negative ions in aqueous solution. It includes enthalpy and Gibbs energy of formation, partial molar entropy, and partial molar heat capacity. The standard state is the hypothetical ideal solution with molality equals 1 mol/kg. 

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The chemistry of plutonium ions in solution has been thoroughly studied and reviewed (30,94—97). Thermodynamic properties of aqueous ions of Pu are given in Table 8 and in the Uterature (64—66). The formal reduction potentials in aqueous solutions of 1 Af HCIO or KOH at 25°C maybe summarized as follows (66,86,98—100) ... 

Shock, E. L., Sassani, D. C., Willis, M. Sverjensky, D. A. (1997). Inorganic species in geologic fluids correlations among standard molal thermodynamic properties of aqueous ions and hydroxide complexes. Geochimica et Cosmochimica Acta,... 

Inorganic species in geologic fluids correlations among standard molal thermodynamic properties of aqueous ions and hydroxide complexes. Geochim. Cosmochim. Acta 61, 907-950. 

In Chapter 14 (Solutions and Their Physical Properties), we have added a section to describe the standard thermodynamic properties of aqueous ions. We use the concepts of entropy and chemical potential in Chapter 13 to explain vapor pressure lowering and why gasoline and water don t mix. 

The problem of measuring the thermodynamic properties of aqueous transition metal ions above 100 C has also received some attention with studies on Fe + complexing with Cl (46), Br (47) and SO - (48) up to 150°C and the formation of anionic hydroxy complexes of Pb2+ up to 300°C (49). 

Equations used to calculate L and 4>CP are taken from K. S. Pitzer, Ion interaction approach theory and data correlation , Chapter 3 in Activity Coefficients in Electrolyte Solutions, 2nd Edition, K. S. Pitzer, Editor, CRC Press, Boca Raton, Florida, 1991. Equations for calculating L, L2, Ju and J2 are summarized in K. S. Pitzer, J. C. Peiper, and R. H. Busey, Thermodynamic properties of aqueous sodium chloride solutions , J. Phys. Chem. Ref Data, 13, 1-102 (1984). 

Several excellent articles have recently been published in which the thermodynamic properties of single ions in aqueous and non-aqueous solvents have been treated thoroughly. Therefore, only a short survey over a) the experimental methods and b) the assumptions for the determination of the free energy of transfer of single ions shall be presented. 

The entropy of dissolved species is approached quite differently. We cannot know (and do not need to know) their absolute entropies. Instead, we consider the dijfferences in S (or AS) between an aqueous species and ion, assuming St for the H" (aq) = 0. Treatment of the thermodynamic properties of aqueous species is addressed in more detail later. 

The thermodynamic properties of aqueous species are for a one-molal concentration of the species (1 mol/kg of solvent water), which, for relatively insoluble species, may be strictly hypothetical. The thermodynamic properties of dissolved ionic species are based on the assumption that the heat capacity, entropy, A/// and AGf of the hydrogen ion [H+(aq)], all equal zero at all temperatures and pressures in other words, it is assumed that AG/ = AH/ = S° 0 for the hydrogen ion and that AG ° = AH/ = AS/ = 0 for the reaction... 

Figure 8.16 Starting point for the derivation of the required equations for the calculation of salt solubilities in organic solvents starting from the tabulated standard thermodynamic properties of the ions in an aqueous solution.

The tables in this chapter include Debye-HUckel parameters for the osmotic coefficient, enthalpy, and heat capacity as a function of temperature parameters for the activity and osmotic coefficients of approximately 270 aqueous strong electrolytes at 25 C parameters for the relative apparent molar and excess enthalpy of %90 strong electrolytes at 25 C a table of parameters for the activity and osmotic coefficients ofss75 binary mixtures with and without common ions and with up to three solutes present and parameters for the thermodynamic properties of aqueous NaCI and H2SO4 as a function of temperature. The author has included references to his earlier papers ivhich also contain valuable data on electrolyte solutions (also see item [121]). 

Table 2.3 Test of the different equations for the standard partial molar volume of aqueous ions (Reproduced from Chemical Geology, A new equation of state for correlation and prediction of standard molal thermodynamic properties of aqueous species at high temperatures and pressures with permission from Elsevier)...

The properties of ions in solution depend, of course, on the solvent in which they are dissolved. Many properties of ions in water are described in Chapters 2 and 4, including thermodynamic, transport, and some other properties. The thermodynamic properties are mainly for 25°C and include the standard partial molar heat capacities and entropies (Table 2.8) and standard molar volumes, electrostriction volumes, expansibilities, and compressibilities (Table 2.9), the standard molar enthalpies and Gibbs energies of formation (Table 2.8) and of hydration (Table 4.1), the standard molar entropies of hydration (Table 4.1), and the molar surface tension inaements (Table 2.11). The transport properties of aqueous ions include the limiting molar conductivities and diffusion coefficients (Table 2.10) as well as the B-coefficients obtained from viscosities and NMR data (Table 2.10). Some other properties of... 

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). 

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