Question

Ostawards dilution law stat's

Answer 1

Ostwald’s dilution law is the application of the law of mass action to weak electrolytes in solution. Suppose an acid HA is dissolved in water, it will ionise as under:

\underset{\underset{C(1- \alpha)} C}{HA} \leftrightharpoons \underset{\underset{C \alpha} 0}{H^+} + \underset{\underset{C \alpha} 0}{a^-} \underset{\underset{(\text{Eq. conc.}} (\text{Initial conc.)}}{}
Applying law of mass action,

K_a = \dfrac{[H^+][A^-]}{[H A]} \\[3mm] \therefore K_a = \dfrac{(C \alpha)(C \alpha)}{C(1- \alpha)} = \dfrac{C \alpha^2}{1- \alpha}
Where K_a is the dissociation (or ionisation) constant of the acid HA and \alpha is its degree of dissociation.

This equation is known as Ostwald’s dilution law equation.