Explain Ostwald's dilution law.

Answer:

Ostwald’s dilution law describes the dissociation constant of the weak electrolyte with the degree of dissociation (α) and the concentration of the weak electrolyte.

A binary electrolyte AB which dissociates into A⁺and B^– ions.

AB ⇌ A⁺ + B^–

(i) For very weak electrolytes, since α <<< 1, (1 – α) = 1

∴ \(K = C\alpha ^{2}\) \(\alpha = \sqrt\frac{K}{C}\)

(ii) Concentration of any ion = √K/V

K =dissociation constant of a weak acid

α = degree of dissociation.

Ostwald’s dilution law states that only at infinite dilution the weak electrolyte undergoes complete ionization.