Molar conductivity

Molar conductivity is defined as conductance of ‘V’ volume of electrolyte present between electrodes having area of cross section and separated by unit length. Therefore, as the dilution increases volume increases and molar conductivity also increases.

For strong electrolyte degree of dissociation is almost 100%. Therefore, on dilution molar conductivity increases because not the number of ions in solution. As the solution becomes dilute, all the ions gets separated and each ion not influenced by other and therefore each ion behaves almost like independent. Therefore, molar conductivity increases.

Molar conductivity at infinite dilution is known as Limiting molar conductivity. This can be calculated for the strong electrolytes by lotting molar conductivity with square root of its concentration and the resulting straight line with negative slope can be extrapolated to y- axis and the corresponding intercept on y-axis is the limiting molar conductivity. But limiting molar conductivity can not be calculated directly because as the dilution increases degree of dissociation of weak electrolyte increases, which increases molar conductivity steeply at low concentrations. Limiting molar conductivity of weak electrolyte can be calculated by “Kohlrausch law “. 

Kohlrausch is defined as “Limiting molar conductivity of an electrolyte can be represented as the sum of the limiting conductivities of cations and ions provided by one mole of electrolyte.“