Question

Which one of the following statements is correct for an electrolyte solution when its concentration is decreased?

• A. Both specific and molar conductances decrease
• B. Both specific and molar conductances increase
• C. Specific conductance increases and molar conductance decreases
• D. Specific conductance decreases and molar conductance increases

Answer 1

The correct option is D Specific conductance decreases and molar conductance increases

Both conductivity and molar conductivity change with the concentration of the electrolyte. Conductivity always decreases with decrease in concentration both, for weak and strong electrolytes. This can be explained by the fact that the number of ions per unit volume that carry the current in a solution decreases on dilution.

The molar conductivity increases with decrease in concentration. This is because the total volume, V, of a solution containing one mole of electrolyte also increases. It has been found that a decrease in k on dilution of a solution is more than compensated by an increase in its volume.

Physically, it means that at a given concentration $\bigwedge m$ can be defined as the conductance of the electrolytic solution kept between the electrodes of a conductivity cell at a unit distance but having an area of cross-section large enough to accommodate sufficient volume of solution that contains one mole of the electrolyte.

Specific conductance decreases and molar conductance increases.