(a) Define molar conductivity of a solution and explain how molar conductivity changes with a change in concentration of solution for a weak and a strong electrolyte.

(b) The resistance of a conductivity cell containing 0.001 M KCl solution at 298 K is Ω 1500 . What is the cell constant if the conductivity of 0.001 M KCl solution at 298 K is 0.146x10^-3 S cm^-1?

Molar conductivity of a solution at a given concentration is the conductance of volume V of a solution containing 1 mole of the electrolyte kept between two electrodes with the area of cross-section A and distance of unit length.

Molar conductivity increases with a decrease in concentration. This is because the total volume V of the solution containing one mole of the electrolyte increases on dilution.

Variation of molar conductivities with dilution:

For strong electrolytes, molar conductivity slowly increases with dilution.

For weak electrolytes, molar conductivity increases steeply on dilution, especially near lower concentrations. The variation of  with  for strong and weak electrolytes is shown in the following plot:

b) Given,

 Conductivity, k = 0.146 x 10^-3 S cm^-1

Resistance, R = 1500 ohm