Question

Explain molar conductivity. The resistance of a cell filled with \( 0.02 \, \text{mol L}^{-1} \) KCl solution is \( 480 \, \Omega \). Calculate the molar conductivity of the solution. (Cell constant = \( 29 \, \text{cm}^{-1} \)).

Hint:

Molar conductivity increases with dilution due to a decrease in interionic attractions.

Answer 1

Molar Conductivity (\( \Lambda_m \)): It is the conductivity of an electrolyte solution per unit concentration: \[ \Lambda_m = \kappa \cdot \frac{1000}{C}, \] where \( \kappa \) is the conductivity and \( C \) is the molarity of the solution. 

Calculation: 1. Conductivity (\( \kappa \)): \[ \kappa = \frac{\text{Cell constant}}{\text{Resistance}} = \frac{1.29}{480} = 0.0026875 \, \text{S cm}^{-1}. \] 2. Molar conductivity (\( \Lambda_m \)): \[ \Lambda_m = 0.0026875 \cdot \frac{1000}{0.02} = 134.375 \, \text{S cm}^2 \text{mol}^{-1}. \]