

Dilution tends to increases the degree of dissociation especially in case of weak acids. Let us understand by the following equation.
Example a weak acid, HA.
HA + H2O ⇔ H3O+ + A-
Dilution means adding more of H2O.
According to Le chatelier principle, this addition will shift equilibrium forward or in the right side direction. This means that dilution increases the degree of dissociation.
