Halides solubility-product constant

Marked differences are observed between the properties of the halides. The trifluorides are stable in air at room temperature and are non-hydroscopic. They are sparingly soluble in water with solubility product constants which vary from 10 for lanthanum to 10 for lutetium (DaDilva and Queimado, 1973). In liquid HF, the solubilities are less than 4x 10 mole/ (Ikrami et al., 1972). At high temperatures the trifluorides react with oxygen and moisture to form the oxide fluorides, ROF, which are stable in air at temperatures greater than 1000°C. Conversion of the fluorides to the oxides may be achieved by heating in steam at 1000°C (Stezowski and Eick, 1970). 

Figure 7-7 illustrates how affects the titration of halide ions. The least soluble product, Agl, gives the sharpest change at the equivalence point. However, even for AgCI, the curve is steep enough to locate the equivalence point accurately. The larger the equilibrium constant for a titration reaction, the more pronounced will be the change in concentration near the equivalence point. 

Table 10. Solubility products of silver halides, and formation constants of dihalogenido complexes of the silver ion in various solvents...

The equilibrium parameters of Lux acid-base reactions in ionic media (solubility products of oxides and acid-base equilibrium constants) are essentially affected by the acidic properties of the molten alkaline halide mixtures, i.e., they are dependent on the constituent cation acidities. Therefore, one should consider the reverse problem - the estimation of the basicity indices of ionic melts on the basis of the calculated equilibrium constants. 

TABLE 14.10 Solubility products, calculated formation constants, and calculated and experimental E° values (V vs NHE) for the silver halides at 298 K. 

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