Question

The degree of dissociation of an electrolyte is :

• A. directly proportional to its concentration
• B. directly proportional to the square of its concentration
• C. inversely proportional to its concentration
• D. inversely proportional to the square root of its concentration

Answer 1

The correct option is D inversely proportional to the square root of its concentration

For a weak electrolyte, the dissociation constant can be written as:

$K_d=\frac{{\alpha }^2}{1-\alpha }C$, where $\alpha$ (degree of dissociation) $<<1$ and C is the concentration of electrolyte.
$\therefore \frac{K_d}{C}=\frac{{\alpha }^2}{1}$.
$\therefore \alpha =\sqrt{\frac{K_d}{C}}$.
$\therefore \alpha \propto \frac{1}{\sqrt{C}}$.

The degree of dissociation is inversely proportional to the square root of concentration.