Pure components strong electrolytes

Solubility of a Pure Component Strong Electrolyte. The calculation of the solubility of a pure component solid in solution requires that the mean ionic activity coefficient be known along with a thermodynamic solubility product (a solubility product based on activity). Thermodynamic solubility products can be calculated from standard state Gibbs free energy of formation data. If, for example, we wished to calculate the solubility of KCI in water at 25 °C,... 

SOLUTION and MIXTURE - There is some confusion between these two terms in geological literature. According to the I.U.P. A.C. (International Union for Pure and Applied Chemistry), the term mixture must be adopted whenever all components are treated in the same manner , whereas solution is reserved for cases in which it is necessary to distinguish a solute from a solvent. This distinction in terminology will be more evident after the introduction of the concept of standard state. It is nevertheless already evident that we cannot treat an aqueous solution of NaCl as a mixture, because the solute (NaCl) in its stable (crystalline) state has a completely different aggregation state from that of the solvent (H2O) and, because NaCl is a strong electrolyte (see section 8.2), we cannot even imagine pure aqueous NaCl. 

Displacement of equilibria in adsorbed layers. If an equilibrium exists in solution between two or more constituent substances, and one of these is adsorbed more strongly than another, that one will be more concentrated in the surface and the equilibrium in the surface layer will be shifted in the direction of that constituent. It often happens, owing to electrolytic dissociation or to hydrolysis, that a single pure substance when dissolved in water consists of such an equilibrium mixture, and if the bulk solution alone were under consideration, an aqueous solution of such a substance would naturally be treated, according to the phase rule, as a two-component system. But when surfaces enter into consideration, unless the ease of adsorption of both the constituents of the equilibrium mixture in solution is identical, the adsorption of each has to be considered separately and consequently the system must be regarded as consisting of three components at least, not two.5... 

The situation has already been described in the preceding paragraph where one of the combining ions comes from the added electrolyte. When both combining ions are natural components of the polymerizing system we have a case of pure termination. Combination of the counter-ion with the active centre is the reason why many sufficiently strong acids and bases cannot be used for the initiation of ionic polymerizations. 

We now leave pure materials and the limited but important changes they can undergo and examine mixtures. We shall consider only homogeneous mixtures, or solutions, in which the composition is uniform however small the sample. The component in smaller abundance is called the solute and that in larger abimdance is the solvent. These terms, however, are normally but not invariably reserved for solids dissolved in Kquids one liquid mixed with another is normally called simply a mixture of the two liquids. In this chapter we consider mainly nonelectrolyte solutions, where the solute is not present as ions. Examples are sucrose dissolved in water, sulfur dissolved in carbon disulfide, and a mixture of ethanol and water. Although we also consider some of the special problems of electrolyte solutions, in which the solute consists of ions that interact strongly with one another, we defer a full study until Chapter 5. The measures of concentration commonly encoimtered in physical chemistry are reviewed in Further information 3.2. 

---