The curves obtained when molar conductivity `lambda_(m)` (along Y-axis) is plotted against the square root of concentration `C^(1//2)` (along X-axis) for two electrolytes 'A' and 'B' are shown.

(a) What can you say about the nature of the two electrolytes ?
(b) How do you account for the increase in molar conductivity `Lambda_(m)` for the electrolytes A and B on dilution ?

Explanation

(a) Electrolyte 'A' is a strong while 'B' is a weak electrolyte.
(b) In case of strong electrolyte, 'A', the ionisation is already complete. With dilution, the interionic forces decrease. Therefore, the ionic mobility increases leading to small increase in the value of `Lambda_(m)`. This continues till limiting value of molar conductance reaches. It is denoted either as `Lambda^(0)` or as `Lambda^(oo)`. In case of weak electrolyte, 'B' the extent of dissociation is very small. It increase with dilution. As a result, the value of `Lambda_(m)` increases with dilution. Since there is an enormous increase in ionisation upon dilution, there is large increase in the value of `Lambda_(m)` when the solution is very dilute. This has been depicted in the curve. In case of electrolyte 'B', the limiting value of the molar conductance (`Lambda_(m)^(0)`) cannot be achieved since the dissociation of the electrolyte is never complete.