Evaluation of Equilibrium Constants

Values of AG° for matty formation reactions are tabulated in standard references. The reported values of AG are not measured experimentally, but are calculated by Eq. (13.16). The detennination of A5 may be based on the tliird law of thennodynamics, discussed in Sec. 5.10. Combination of valnes from Eq. (5.40) for the absolute entropies of the species taking part in the reaction gives the valne of AS. Entropies (and heat capacities) are also commonly determined from statistical calcnlations based on spectroscopic data.  

Values of for a hmited number of chemical compounds are listed in Table C. 4 of 

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Alcock, R. M. Hartley, F. R. Rogers, D. E., A damped non-linear least-squares computer program (dalsfek) for the evaluation of equilibrium constants from spectrophotometric and potentiometric data, J. Chem. Soc. Dalton Trans. 115-123 (1978). 

Association reactions can be characterized by equilibrium constants. Experimental determination of equilibrium constants for each step in an association reaction provides vital information about the properties of the associating system. In particular, the mode of association (e.g., monomer-dimer, monomer-tetramer, indefinite), and the strength of the association (that is, the degree to which various oligomers can exist at various total concentrations) can be obtained. The evaluation of equilibrium constants over a range of solution conditions (such as salt concentration and temperature) can be used to obtain information on the enthalpy and entropy of the various steps in the association and the types of bonds involved in the assembly process. Note that this information can be obtained in the complete absence of structural information, although, of course, any available structural information can be used to aid in the interpretation of the thermodynamic data. 

The solvation of chromium(llI) ion in certain mixed-solvent systems has been studied in experiments which are relatively free of ambiguity. The exchange of solvent molecules between the mixed solvent and the solvated species Cr(OH2)w (So)n3+ (So = organic solvent component) is a very slow process. The species with solvation shells having different compositions can be separated from one another by column ion-exchange procedures. Analytical procedures based upon such separations allow evaluation of equilibrium constants for reactions involving replacement of coordinated water by the polar organic component. These equilibrium constants are reviewed in this chapter with attention focused upon the dependence of the equilibrium constants upon solvent composition, and the relationship of relative values of the equilibrium constants to the statistically expected values. 

LiF(g) which is consistent with the literature values listed in the table below. Due to lack of knowledge of the fragmentation patterns, the relative ionization cross sections of the ionic species formed in the mass spectrometer, and the molecular constants of the LiF polymers, the evaluation of equilibrium constants used to calculate A H" involves considerable uncertainty. In order to solve this problem more research work seems necessary. 

J. Stary, ed.. Critical Evaluation of Equilibrium Constants Involving 8-Hydroxyquinoline and Its Metal Chelates. Oxford Pergatnon, 1979. 

Ludwig, Chr. GRIFIT, A Program for Solving Speciation Problems Evaluation of Equilibrium Constants, Concentrations and other Physical Parameters, Internal Report, University of Berne, 1992. 

Star, J., Zolotov, Yu. A., and Petnikhin, O. M. (1979) Critical Evaluation of Equilibrium Constants Involmng S-Hydroxyquinoline and Its Metal Complexes, Pergamon, Oxford (lUPAC Chemical Data Series No. 24). 

Eor complexation studies with a guest that exhibits intermolecular self-association, the association should also be considered in the analysis. An example for this is the complexation of phenothiazine dyes with CDs. The dyes form non-fluorescent dimers. The monomers form 1 1 complexes with /i-CD, while the dimers form 1 1 complexes with y-CD. Evaluation of equilibrium constants... 

Silvestri, F. Talarico, and M. Vicedomini, Ann. Chim. (Rome), 1979, 69, 19 Stary, Yu.A. Zolotov, and O.M. Petrukhim, Critical Evaluation of Equilibrium Constants Involving 8-Hydroxvquinoline and its Metal Chelates, Pergamon Press, Oxford, 1979... 

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