Solution formation enthalpy diagram

Figure 13.4A is an enthalpy diagram for the formation of such a solution. If the sum of the endothermic terms is larger than the exothermic term, A//soin is positive that is, the process is endothermic (Figure 13.4B). However, if AZ/join is highly positive, the solute may not dissolve to any significant extent in that solvent.

The Frost diagrams for the first series of the d block elements in acidic solution, pH = 0, given in Figure 7.11(b) show many similarities with the variation of the enthalpy of formation of the oxides. Only the oxidation states observed for solid oxides are included. 

Calorimetry is generally a high-accuracy method for determination of thermodynamic properties. A particular variant is the high-temperature drop calorimetry where the oxide phase is dissolved in a suitable melt and enthalpies of formation from oxides are evaluated from the thermal effect. Drop-calorimetry data (Rian 1992, Zhou and Navrotsky 1992, Lamberti et al. 1997) obtained for phases fiom the R(0)-Ba(0)-Cu(0) phase diagram are summarized in table 26. Similar, but much more scattered data were obtained in numerous early studies by various aqueous-solution calorimetry techniques for recent more precise data by the latter technique on RBa2Cu306.9 (R = Gd, Ho, Y), see Matskevich and McCallum (1999). Only a few adiabatic calorimetry studies have focused on determination of thermodynamic properties of the superconducting phases. 

Schick s work includes the study of borides, carbides, nitrides, and oxides of some elements in Groups IIA, IIIB, IVA, IVB, VB, VIIB, and VIII as well as selected rare earths and actinides. As far as possible, the tables have been made compatible with the JANAF tables. Among the subjects treated are phase diagrams, heat capacities, enthalpies, entropies, enthalpies of phase transformation, formation, and reaction, melting temperatures, triple points, free energies of formation, vapour pressures, compositions of vapour species, ionization and appearance potentials, e.m.f. of cells, and enthalpies of solution and dilution. Volume 1 summarizes the techniques used to analyse data and cites the data analysed, and Volume 2 gives tables of values produced by this study. 

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