Applications of Distribution Law - QS Study

Applications of Distribution Law

The distribution law can be applied to a number of physical and chemical processes. Thus association of the solute in one phase can be ascertained, and degree of association and therefore, the molecular mass of the solute in a given liquid can be found out. The law may also be used to determine the degree of dissociation of acids, bases or salts in a solvent. Other examples are given below;

(a) The degree of hydrolysis of substances can be conveniently studied. The hydrolysis of aniline hydrochloride in water can be followed from the distribution of aniline hydrochloride between water and benzene. Thus for this reaction,

Aniline hydrochloride (Salt) + Water (H2O) ↔ Aniline (Base) + Hydrochloric acid (Acid)

Thus, Kh = {[Base] x [Acid]} / {[Salt] x [H2O]}

By applying the principle of equilibrium it can be shown that,

Kh = {C12 (1+vK)} / {C2 – C1(1+vK)}

where C1 is the concentration of the base in aqueous layer (C1 and C2 are expressed in Mol L-1), C2 the original concentration of the salt, K the distribution co-efficient and v is the volume of benzene in litres added to 1 litre of water.

(b) The formula of the complex CuSO4.4NH3 was confirmed from the studies of distribution of ammonia between chloroform and aqueous Copper Sulphate Solution.

(c) Another example of the application of the distribution law can be demonstrated by finding the equilibrium constant for the equilibrium.

Among the applications of Nernst’s distribution law, the most significant and attractive one is the extraction of a material dissolved in one solvent by another solvent, the two solvents being partially miscible or immiscible.