Sodium thermodynamic data

Thermodynamic data show that the stabilities of the caesium chloride-metal chloride complexes are greater than the conesponding sodium and potassium compounds, and tire fluorides form complexes more readily tlrair the chlorides, in the solid state. It would seem that tire stabilities of these compounds would transfer into tire liquid state. In fact, it has been possible to account for the heats of formation of molten salt mixtures by the assumption that molten complex salts contain complex as well as simple anions, so tlrat tire heat of formation of the liquid mixtures is tire mole fraction weighted product of the pure components and the complex. For example, in the CsCl-ZrCU system the heat of formation is given on each side of tire complex compound composition, the mole fraction of the compound... 

Figure 7.4 Thermodynamic data needed in evaluation of the enthalpy of formation of MX(s). (a) Lattice enthalpy of sodium halides (b) lattice enthalpy of alkali iodides (c) electron gain and dissociation enthalpies of halides (d) ionization and atomization enthalpies of alkali metals.

Although the entire discussion of electrochemistry thus far has been in terms of aqueous solutions, the same principles apply equaly well to nonaqueous solvents. As a result of differences in solvation energies, electrode potentials may vary considerably from those found in aqueous solution. In addition the oxidation and reduction potentials characteristic of the solvent vary with the chemical behavior of the solvent. as a result of these two effects, it is often possible to carry out reactions in a nonaqueous solvent that would be impossible in water. For example, both sodium and beryllium are too reactive to be electroplated from aqueous solution, but beryllium can be electroplated from liquid ammonia and sodium from solutions in pyridine. 0 Unfortunately, the thermodynamic data necessary to construct complete tables of standard potential values are lacking for most solvents other than water. Jolly 1 has compiled such a table for liquid ammonia. The hydrogen electrode is used as the reference point to establish the scale as in water ... 

Physical chemical studies of dilute alkali metal-ammonia solutions indicate the principal solution species as the ammoniated metal cation M+, the ammoniated electron e , the "monomer M, the "dimer" M2 and the "metal anion" M. Most data suggest that M, M2, and M are simple electrostatic assemblies of ammoniated cations and ammoniated electrons The reaction, e + NH3 - lf 2 H2 + NH2 is reversible, and the directly measured equilibrium constant agrees fairly well with that estimated from other thermodynamic data. Kinetic data for the reaction of ethanol with sodium and for various metal-ammonia-alcohol reductions of aromatic compounds suggest that steady-state concentrations of ammonium ion are established. Ethanol-sodium reaction data allow estimation of an upper limit for the rate constant of e + NH4+ 7, H2 + NH3. 

High temperature thermodynamic data are available only for three sulfites calcium, potassium, and sodium. Most sulfites are fairly unstable, decomposing at relatively low temperatures. The decomposition reactions are not always exactly known, with diverse decomposition products, including sulfur, being reported. There are two major decomposition reactions (1) decomposition to the oxide and S02, and (2) oxidation-reduction (disproportionation) to the sulfate and oxide and S02, i.e.,... 

The ionic species present in the electrolyte appear to be Na+, A1F63 , A1F4 , F and certain A1—O—F complexes (see above). The fact that sodium is present as free ions, whereas aluminum is bound in complexes, and the fact that the sodium ion is the carrier of current, have led many authors to the assumption that sodium is the primary discharge product at the cathode. However, the thermodynamic data favor primary aluminum deposition on aluminum in cryolite melts. 

Kelley (1 ). The adopted value is -341.1 kcal mol" which was obtained by rounding the reported value of Mah and Kelley (1.). For more details refer to the V O Ccr) table (2). Charlu and Kleppa (3 ) reported a enthalpy of formation value at A H (298.15 K) -342.4 0.78 kcal mol" based on oxidation studies to V OgCcr) in a high temperature microcalorimeter. The combustion by this technique yielded complete oxidation to VgO Ccr) as opposed to the method of Mah and Kelley ( ), whereby A H for V20 (cr) was determined simultaneously with that for VgO Ccr) due to incomplete combustion of V(cr). A combustion study by Siemonsen and Ulich (4) led to the reported value of -342 2 kcal mol" for A H (V20, cr, 293 K). Additional thermodynamic data which relate 2 3 ° with VgO Ccr) or V20g(cr) is contained in the sodium oxide fusion studies by Mixter (5), the H2O-H2 equilibrium study by Muller (6), the CO-CO2 equilibrium study by Spencer and Justice (7), and the reduction of V O Ccr) with SO2 by Flood and Kleppa ( ). See V20g(cr) table for some additional information (2 ). 

The coal ash deposits on boiler tubes have frequently a separate zone structure with a sulphate rich layer up to 2 mm thick under the matrix of sintered ash (3 ). The outer layer is porous and it constitutes a pathway for the enrichment of alkali-metals in the deposit layer next to tube suface. The diffusable species may be sulphate, chloride, oxide or hydroxide, but the thermodynamic data W and the results of deposition measurements in coal fired boilers (Figure 3) suggest that sodium and potassium sulphates are the principal vapour species which diffuse through a porous matrix of silicate ash deposit. 

The species (NaBr)j(g) (i = 1,2,3) were identified by Hilpert and Miller [463] in the vapor over sodium bromide. A consistent set of thermodynamic data based on a second- and third-law evaluation was obtained unlike Refs. 448,464. The mole fraction of the dimer at the mean temperature of 750 K of Hilpert and Miller s measurements is 52 percent smaller than that given by the JANAF tables [90]. 

The complexation in the Nal-Sclg system (cf. Table 20) has been investigated by us for the first time by the use of two-compartment Knudsen cells. By this means a substantially improved assignment of the various ions in the mass spectrum to their neutral precursors is rendered possible, which is a pre-requisite for the determination of reliable thermodynamic data. Two-compartment Knudsen cells were also used for the study of the systems NaX-SnXj (X = Q, Br, I) (Table 20) as well as the systems NaBr-SnIj and SnBr2-Snl2 (Table 21) due to the different volatilities of the sodium and tin halides and in order to elucidate fragmentation patterns especially for systems with mixed anions. 

The unplugging temperature is close to the saturation temperature for the impurity present in the sodium Nevertheless, it confers a boundary which is higher than the saturation temperature based on thermodynamic data and the cinetics of the dissolution in the pellet. 

It would be of interest to try a quantitative theory, based on similar ideas as those which have been developed by Gee for the swelling of rubber in mixtures of two solvents (cf. Section 6, b. 2a). The solutions of sodium hydroxide of various concentrations should thereby be regarded as solvent mixtures of different composition and their thermodynamical data studied. 

Differential scanning calorimetry provides numerical thermodynamic data and is frequently the main technique used to determine phase diagrams [40,46-57]. Some surfactant systems studied by DSC analysis in the literature are soap-water [41-43], dipalmitoylphosphatidyl choline-water [17,44], sodium dodecylsul-fate-water [13], CwPO-water [1,2,6], perfluorosurfactants-water [45], and dioc-tadecyldimethylammonium bromide-water [46]. 

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