Explain the variation in molar conductivity of weak electrolyte with concentration.

Explanation

Variation of molar conductivity with concentration for strength electrolyte: In case of strong electrolytes, molar conductance increases slowly with dilution and there is a tendency for molar conductivity to approach a certain limiting value when the concentration approaches zero. The molar conductivity when the concentration approaches zero (infinite dilution) is called molar conductivity at infinite dilution. It is denoted by `Lamda_(m)^(@) or Lamda_(m)^(oo)`. Thus `Lamda_(m)= Lamda_(m)^(0)` when `C rarr O` (at infinite dilution) the variation of molar conductivity with concentration may be given by the expression.
`Lamda_(m) =Lamda_(m)^(0) - b sqrtc`
b is constant `Lamda^(@)` is called molar conductivity.

Variation of molar conductivity with conc. for weak electrolytes: the weak electrolytes dissociate to a much lesser extent as compared to strong electrolytes. Therefore, the molar conductivity is low as compared to that of strong electrolytes. However, the variation of `Lamda_(m)` with `C^((1)/(2))` is very large and so much that we can not obtain molar conductance at infinite dilution `(Lamda_(m)^(@))` by extrapolation of the `Lamda_(m)` verses `C^((1)/(2))` plots. The behavior of weak electrolyte such as `CH_(3)COOH` is shown in figure.