Thermodynamic properties aqueous ions

This table contains standard state thermodynamic properties of ions and neutral species in aqueous solution. It includes enthalpy and Gibbs energy of formation, entropy, and heat capacity, and thus serves as a companion to the preceding table, Standard Thermodynamic Properties of Chemical Substances . The standard state is the hypothetical ideal solution with molality m = 1 mol/kg (mean ionic molality in the case of a species which is assumed to dissociate at infinite dilution). Further details on conventions may be found in Reference 1. 

Aqueous Solvation.—A review, covering the 1968—1972 publications, deals with physical properties, thermodynamics, and structures of non-aqueous and aqueous-non-aqueous solutions of electrolytes, and complete hydration limits. Thermodynamic aspects of ionic hydration also reviewed include the thermodynamic theory of solvation the molecular interpretation of ionic hydration hydration of gaseous ions (AG s, H s, and AA s) thermodynamic properties of ions at infinite dilution in water, solvent isotope effect in hydration reference solvents and ionic hydration and excess properties. A third review on the hydration of ions emphasizes the structure of water in the gaseous, liquid, and solid states the size of ions and the hydration numbers of ions and the structure of the hydrated shell from measurements of mobility, compressibility, activity, and from n.m.r. spectra. Pure water and aqueous LiCl at concentrations up to saturation have been examined by neutron and X-ray diffraction. For the neutron studies LiCl and D2O are employed. The data are consistent with a simple model involving only... 

In addition to the thermodynamic properties of ions, Latimer gives extensive tables for the properties of elements in the crystalline and gaseous states and for inorganic compounds in the form of crystals and in aqueous solution. 

Thermodynamic properties of ions in nonaqueous solvents are described in terms of the transfer from water as the source solvent to nonaqueous solvents as the targets of this transfer. These properties include the standard molar Gibbs energies of transfer (Table 4.2), enthalpies of transfer (Table 4.3), entropies of transfer (Table 4.4) and heat capacities of transfer (Table 4.5) as well as the standard partial molar volumes (Table 4.6) and the solvation numbers of the ions in non-aqueous solvents (Table 4.10). The transfer properties together with the properties of the aqueous ions yield the corresponding properties of ions in the nonaqueous solvents. 

We have now acquired all the tools with which to perform one of the most practical calculations of chemical thermodynamics determining the equilibrium constant for a reaction from tabulated data. Example 13-10, which demonstrates this application, uses thermodynamic properties of ions in aqueous solution as well as of compounds. An important idea to note about the thermodynamic properties of ions is that they are relative to H" (aq), which, by convention, is assigned values of zero for AfH°, AfG°, and S°. This means that entropies listed for ions are not absolute entropies, as they are for compounds. Negative values of S° simply denote an entropy less than that of H (aq). 

In Chapter 7, we learned how to combine thermodynamic properties of different substances to calculate the heat absorbed or released by a reaction. In Chapter 13, we learned how to combine thermodynamic properties of different substances to calculate equilibrium constants for reactions. Many chemical reactions occur in aqueous solution and involve ions. To be able to calculate heats of reaction or equilibrium constants for such reactions, we need values for the thermodynamic properties of the aqueous ions involved. In this section, we discuss the standard thermodynamic properties of ions in solution, particularly with respect to how their values are established and interpreted. 

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). 

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) ... 

Criss, C.M. Cobble, J.W., "Thermodynamic Properties of High Temperature Aqueous Systems. IV Entropies of the Ions up to 200°C and the Correspondence Principles", JACS, 1964, 86,... 

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). 

Tanger J. C. and Helgeson H. C. (1988). Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures Revised equation of state for the standard partial molal properties of ions and electrolytes. Amer. Jour. Set, 288 19-98. 

J. W. Cobble, High-temperature aqueous solutions. Science, 152, 1479-1485 (1966) C. M. Criss and J. W. Cobble, The thermodynamic properties of high temperature aqueous solutions. IV. Entropies of the ions up to 200 °C and the correspondence principle. V. The calculation... 

Note that these single ion values were obtained from entirely different extrathermodynamic assumptions elaborate extrapolation procedure in the case of the water-acetone mixtures, and tetraphenylboron assumption for the water-THF mixture. n-Bu4N+ and Br showed similar behavior in the two binary systems studied this might be the consequence of the similarity between the thermodynamic properties of the two aqueous binaries e.g., both are typically aqueous systems with AHE < T ASE. ... 

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). 

It is possible to compare direct measurements of relative stabilities of isomeric ions with comparisons of nonisomeric ions by use of a group additivity scheme. Group additivity schemes have been developed by Benson for heats of formation (and other thermodynamic properties) of organic molecules in the gas phase,40 and by Guthrie to represent free energies of formation in aqueous solution.38 In both cases, energies of unstrained hydrocarbons accurately correspond to a sum of contributions from primary, secondary, tertiary, and quaternary carbons CH3, CH2, CH, and C. 

This section is largely devoted to the results of thermodynamic studies of equilibria in aqueous solution involving hydrated cations M"+(aq), ligands and the complexes formed by these. Some of the thermodynamic properties of M +(aq) ions have already been discussed... 

The FREZCHEM model was designed to characterize aqueous electrolyte solutions. To work properly, there must always be ions in solution, even if only hypothetical. To simulate pure water, pure gas hydrate, pure ice, or other nonion equilibria, you need to add minor concentrations of ions (e.g., Na = Cl = 1 x 10 6m). Such minor concentrations do not significantly affect the thermodynamic properties, but they do allow for proper model calculations. 

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. 

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. 

The synthesis of HBr04 and rubidium and potassium salts was accomplished, using oxidation of bromate by XeF2 or (preferably) molecular fluorine in aqueous solution.19 Spectral studies20 show that the perbromate ion is tetrahedral in both the solid-state and aqueous solutions. The thermodynamic properties and thermal decomposition of individual salts are discussed under each element. A more general article on various properties of the perbromates was published by Herrell and Gayer.21... 

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. 

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,... 

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 bare proton has an exceedingly small diameter compared with other cations, and hence has a high polarising ability, and readily forms a bond with an atom possessing a lone pair of electrons. In aqueous solution the proton exists as the H30+ ion. The existence of the H30+ ion in the gas phase has been shown by mass spectrometry [4], and its existence in crystalline nitric acid has been shown by NMR [5], Its existence in aqueous acid solution may be inferred from a comparison of the thermodynamic properties of HC1 and LiCl [6]. The heat of hydration of HC1 is 136 kcal mole"1 greater than that of LiCl, showing that a strong chemical bond is formed between the proton and the solvent, whereas the molar heat capacity, molar volume and activity coefficients are similar,... 

Tetraalkylammonium salts are the most common electrolytes for the non-aqueous solvent systems and high molecular weight ammoniums have been used for the ion-pair extractant. The thermodynamic properties of the salts such as partition equilibria, solubility, ion-pair formation etc. have been studied in a variety of solvents. The detailed equilibria or structure of ion pair, however, are not fully elucidated. 

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