Question

A conductivity cell with two electrodes (dark side) are half filled with infinitely dilute aqueous solution of a weak electrolyte. If volume is doubled by adding more water at constant temperature, the molar conductivity of the cell will -

• A. increase sharply
• B. remain same or can not be measured accurately
• C. decrease sharply
• D. depend upon type of electrolyte

Answer 1

Answer: (B)

remain same or can not be measured accurately

Answer 2

The solution is already infinitely dilute, meaning the molar conductivity is at its maximum value. Adding more water will not dilute the solution further; therefore, there will be no change in molar conductivity. It will remain the same.
$\text{Molar conductivity } (\Lambda_m) \propto \frac{\kappa}{c}$
where $\kappa$ is the conductivity and $c$ is the concentration. For infinitely dilute solutions, $c$ is already approaching zero, and $\Lambda_m$ becomes constant.