Transfer Thermodynamics into Nonaqueous Solvents

Having established in the previous sections the thermodynamics of ion hydration, attention may now be turned to the thermodynamics of the solvation of the ions in nonaqueous solvents. As mentioned before, it is expedient to deal not with the solvation process of ions in the ideal gas phase going into the nonaqneous solvents, but to deal with their transfer from water (W) as the sonrce solvent to the nonaqueous solvent as the target solvent (S)  

The transfer thermodynamics can be measured directly in many cases and more accurately than the solvation thermodynamics proper, and Ajy ) is then a fairly small difference between two large numbers. If required, A j y (P-, S) = A y (P, W)-i-A,y (P, W S) can be readily reconstituted. 

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Thermodynamics of Transfer of Ions into Nonaqueous Solvents... 

In this chapter some aspects of the present state of the concept of ion association in the theory of electrolyte solutions will be reviewed. For simplification our consideration will be restricted to a symmetrical electrolyte. It will be demonstrated that the concept of ion association is useful not only to describe such properties as osmotic and activity coefficients, electroconductivity and dielectric constant of nonaqueous electrolyte solutions, which traditionally are explained using the ion association ideas, but also for the treatment of electrolyte contributions to the intramolecular electron transfer in weakly polar solvents [21, 22] and for the interpretation of specific anomalous properties of electrical double layer in low temperature region [23, 24], The majority of these properties can be described within the McMillan-Mayer or ion approach when the solvent is considered as a dielectric continuum and only ions are treated explicitly. However, the description of dielectric properties also requires the solvent molecules being explicitly taken into account which can be done at the Born-Oppenheimer or ion-molecular approach. This approach also leads to the correct description of different solvation effects. We should also note that effects of ion association require a different treatment of the thermodynamic and electrical properties. For the thermodynamic properties such as the osmotic and activity coefficients or the adsorption coefficient of electrical double layer, the ion pairs give a direct contribution and these properties are described correctly in the framework of AMSA theory. Since the ion pairs have no free electric charges, they give polarization effects only for such electrical properties as electroconductivity, dielectric constant or capacitance of electrical double layer. Hence, to describe the electrical properties, it is more convenient to modify MSA-MAL approach by including the ion pairs as new polar entities. 

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