Alkali metals thermodynamic parameters

The nonnuclear chemistry of Fr reduces to studies of coprecipitation in which Fr shows the behavior of the heavier alkali metal. Coprecipitation is followed by ion exchange to concentrate Fr Physical (mp, density, crystal parameters) and chemical (thermodynamics, solvation entropies) properties are theoretically derived or extrapolated from the trends exhibited by the other alkali metals. 

The thermodynamic parameters and relative cation selectivity of some alkali and heavy metal cations with 1,5,14,18-tetraselena-8,11,21,24-tetracyclohexacosane 47 (selena-26-crown-8) were investigated for the first time by titration calorimetry in water-MeCN (l 24v/v) at 25°C to show the contrasting complexation behavior between Ag+ and alkali Tl+ and a very high Ag+ selectivity, originating from the exclusive contribution of the enthalpy term probably owing to the partially covalent interaction between Ag+ and Se-donor <1999JCM284>. 

It should be noted that the materials are synthesized under non-equilibrium conditions as the experiments are performed in a dynamic vacuum, and the local vapour pressure of the alkali metal is unknown. The rate and extent of reaction will depend on the nature of the alkali metal, the temperature of the film and the presence of residual ambient gas impurities, which are not controlled in these preliminary experiments. At present, the effect of these variables on the conductivities cannot be assessed. Synthesis in a closed system will be required to determine the relevant thermodynamic parameters. 

Table 2.2. Thermodynamic parameters of melting of some alkali metal halides...

According to the Lorentz-Lorenz equation (4.3.21) for the molar refraction at optical frequencies, Y is directly proportional to the molecular polarizability p. The Koppel-Palm equation has also been applied to the analysis of solvent effects on thermodynamic quantities related to the solvation of electrolytes [48, 49]. In the case of the systems considered in table 4.11, addition of the parameter X to the linear equation describing the solvent effect improves the quality of the fit to the experimental data, especially in the case of alkali metal halide electrolytes involving larger ions. The parameter Y is not important for these systems but does assist in the interpretation of other thermodynamic quantities which are solvent dependent [48, 49]. Addition of these parameters to the analysis is only possible when the solvent-dependent phenomenon has been studied in a large number of solvents. 

ZrCl has a homoatomic-layer structure sequenced Cl-Zr-Zr-Cl. Each Zr atom has three neighbours in the adjacent sheet at 3.09 A, six more in the same sheet at 3.42 A and three chlorine atoms on the other side at 2.63 A. Weak chlorine-chlorine interactions between sheets at 3.61 A contrast with the strong metal-metal binding within sheets. These structural features account for the graphitic nature and anisotropic electrical conduction of ZrS. Thermodynamic parameters have been obtained for the reduction of zirconium chlorides. The reaction of ZrC with a melt containing alkali-metal chlorides and titanium chlorides has been investigated. ... 

Novozhilov et al. studied the solubility of HC1 in molten alkali- and alkaline earth metal chlorides [268, 269] and found the solubility of HC1 in these melts to obey Henry s law. The thermal dependences of the solubility (the Henry coefficient values) of HC1 in molten alkaline earth metal chlorides, which are exposed to the pyrohydrolysis, are presented in Fig. 2.5.3. The dependences are close to linear anOd their treatment by the least-squares method allows the calculation of the thermodynamic parameters of HC1 dissolution in the chloride melts. These values are presented in Table 2.5.2. 

Thermodynamic parameters of HC1 dissolution in molten alkali-metal chlorides... 

All the routines described for the determination of the thermodynamic (concentration) parameters in metal oxide solutions include some indirectly obtained values. For example, the equilibrium concentration of metal cations is calculated proceeding from the quantity of the oxide-ion donor consumed for titration (precipitation). Direct determination of the concentration of metal cations in the melt (if it is possible) allows one to obtain more correctly the obtained solubility product values. Our paper [332] reports a method for correction of the solubility product values for oxides on the basis of the potentiometric titration data. The modification of the standard routine consists of the simultaneous use of two indicator electrodes, one of which is the membrane oxygen electrode and the other is a metal electrode, reversible to the cations the oxide consists of. This routine was used to estimate the solubility products of copper(I) and nickel(II) oxides in the molten KCl-NaCl equimolar mixture at 700 °C. Investigation of Cu20 by the proposed method is of considerable importance since, as will be shown further, the process of dissociation/dissolution of copper(I) oxide in molten alkali-metal halides differs from the generally accepted one which was considered, e.g. in Ref. [119]. 

The thermodynamic parameters of hydration for many ions have been determined [121,125,126]. Table 3 gives the values of the standard molar Gibbs energy of hydration AGh and standard molar enthalpy of hydration AH , at 25°C for the alkali metal cations. The tabulated values are based on the respective choices A= - 1056 kj/mol and AHh(H ) = -1103 kj/mol, which result from the extrathermodynamic assumption that the thermodynamic parameters of the tetraphenylarsonium cation and tetraphen-ylborate anion are equal [127]. This reasonable and useful assumption, often... 

Comparable recent detailed reviews of the actinide halides could not be found. The structures of actinide fluorides, both binary fluorides and combinations of these with main-group elements with emphasis on lattice parameters and coordination poly-hedra, were reviewed by Penneman et al. (1973). The chemical thermodynamics of actinide binary halides, oxide halides, and alkali-metal mixed salts were reviewed by Fuger et al. (1983), and while the preparation of high-purity actinide metals and compounds was discussed by Muller and Spirlet (1985), actinide-halide compounds were hardly mentioned. Raman and absorption spectroscopy of actinide tri- and tetrahalides are discussed in a review by Wilmarth and Peterson (1991). Actinide halides, reviewed by element, are considered in detail in the two volume treatise by Katzet al. (1986). The thermochemical and oxidation-reduction properties of lanthanides and actinides are discussed elsewhere in this volume [in the chapter by Morss (ch. 122)]. 

Table 6 Comparison of the macrocyclic effect and differences in the thermodynamic parameters for complexes of selected alkali and divalent metal ions with pentagl3raie and [ISJcrown-b."...

The enolate salts, H2C=CH(OM), have been studied at various levels of theory for all of the alkali metals. Several structural and thermodynamic parameters are reported, and the effect of the restriction of enolate resonance by attachment of the cation is described. 

Barriers to rotation around the Cca —N bonds have been determined experimentally for diaminocarbenes (3) and (4) and their protonated and lithiated counterparts the possible involvement of lithium or a proton in the dimerization of these acyclic diaminocarbenes was also reported. A computational study of the dimerization of diaminocarbenes has been performed via rate constant calculations using general transition-state theory calculations. Such a dimerization has been shown to be a rapid equilibrium between the carbenes and the tetra-A-alkyl-substituted enetetramines (5), by characterization of metathesis products when two different tetramines were mixed. The thermodynamic parameters of this Wanzlick equilibrium have been determined for the A-ethyl-substituted compound the enthalpy of dissociation has been evaluated at 13.7kcalmol and the entropy at 30.4calmor K . Complex-ation of diaminocarbenes by alkali metals has been clearly established by a shift of the C NMR signal from the carbene carbon of more than 5 ppm. ... 

Eor alkali metal compounds used as initiators, the active species of polymerization was shown to be an alkali metal alcoholate for the aliphatic cyclic carbonates [24] and an alkali metal phenolate for the aromatic cyclic carbonates [29]. The time required to shift from kinetic control to thermodynamic control is about a few minutes when the polymerization of aliphatic cyclic carbonates is performed at 25 °C in toluene solution. The larger the alkali-metal counterion, the faster the polymerization and the smaller the selectivity parameter, = kp/kb-... 

The experimental and theoretical studies on alkali halides are discussed and summarized in a book edited by Davidovits and McFadden [434]. Molecular parameters and thermodynamic properties including partial pressures are given for alkali halides and metal dihalides by Brewer and Brackett [43 S] as well as Brewer et al. [436], respectively. 

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