Sparingly soluble electrolytes

A plausible deduction of the solubility product relation is the following. When excess of a sparingly soluble electrolyte, say silver chloride, is shaken up with... 

For the growth of calcite at 25°C and with y = 97 mJ m 2,Pk 6 x 10 5, i.e. 0.006%. This amounts to approximately 105 kinks per metre of step. Nielsen and Christoffersen [1] have estimated that, for low molecular weight, sparingly soluble electrolytes, Pk is in the range of 8-0.7%. Hence, an equilibrium surface at this temperature is expected to have a significant number of kink sites along a step. 

Thus it can be stated that, in a saturated solution of a sparingly soluble electrolyte, the product of concentrations of the constituent ions for any given temperature is constant, the ion concentration being raised to powers equal to the respective numbers of ions of each kind produced by the dissociation of one molecule of the electrolyte. This principle was stated first by W. Nernst in 1889. 

Determination of Solubilities of Sparingly Soluble Electrolytes.— If a slightly soluble electrolyte dissociates in a simple manner, it is possible to calculate the saturation solubility from conductance measure-... 

X 10 equiv. per liter, but direct determination gives 2.22 X 10 equiv. per liter. The difference is partly due to incomplete dissociation and partly to the formation of complex ions. In other words, the lanthanum oxalate does not ionize to yield simple La+ "+ and C2O4 ions, as is assumed in the conductance method for determining the solubility in addition complex ions, containing both lanthanum and oxalate, are present to an appreciable extent in the saturated solution. It is necessary, therefore, to exercise caution in the interpretation of the results obtained from conductance measurements with saturated solutions of sparingly soluble electrolytes. 

The solubility of a sparingly soluble electrolyte in water is often expressed in terms of the concentration solubility product, Kc. To take the simplest ease, if one molecule of such an electrolyte dissociates in solution into x cations and y anions according to the equation... 

The solubility of sparingly soluble electrolytes in water, with the exception of the salts of weak acids or bases, may be determined from conductivity measurements on their saturated solutions. A variety of commercial instruments are now available for this purpose and experimental details may be found in handbooks of practical physical chemistry, e.g. Findlay, 1973 Matthews, 1985. 

Supersaturations in aqueous solutions of sparingly soluble electrolytes are best expressed in terms of the solubility product, e.g. 

Solubility measurements may advantageously replace emf methods for the determination of AsoiGy values and related quantities of sparingly soluble electrolytes, such as the Gibbs energy of transfer from a solvent S to a solvent S ... 

Let us consider the solubility equilibrium of a sparingly soluble electrolyte AgCl in water ... 

The equilibrium constant for electrolytes is also called the solubility product Ksp. For sparingly soluble electrolytes such as AgCl, even at saturation, the solution is very dilute and w 1. In this limiting case the solubility product... 

The equilibrium constant for the dissolving of a sparingly soluble electrolyte is called the solubility product constant. The solubility product constant of lithium carbonate is... 

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