Interionic attractions:

The conductance of a solution depends on the number of ions and the speed with which the ions move in solution. In case of strong electrolytes, a number of ions are the similar at all dilutions (since strong electrolytes are fully ionized) and the variation of equivalent conductance along with dilution is therefore because of the change in the speed of the ions with dilution. Within a concentrated solution of like electrolytes, the interionic attractions between the oppositely charged ions would be quite appreciable.

The ions may also form some ion-pairs of the type A⁺B ^- that would not contribute to the conductance. Those interionic forces considerably lower the speed of the ions and hence the conductivity of the solution. Since the dilution is raise the interionic attractions decrease along with the result that the ions will move more freely and independently of their co-ions and thus increasing the equivalent conductance with dilution. At infinite dilution, the ions are quite far apart, the interionic attractions are almost absent and each ion moves completely independent of its co-ions. The molar conductivity then approaches a limiting value at infinite dilution and represents the conducting power of 1 mole of the electrolyte when it is completely split up into ions. It is denoted through Λ∞.

It can be concluded that in case of weak electrolytes, the increase in molar conductivity with dilution is mainly because of (a) an increase in the number of ions in the solution (degree of ionization increases with dilution), and (b) smaller interionic attractions at higher dilutions.