Define conductivity and molar conductivity for the solution of an electrolyte. Discuss their variation with concentration.
Conductivity (κ) is defined as the conductance of one unit volume of solution kept between two electrodes. It depends on the concentration of the electrolyte, nature of solvent, and temperature. Molar conductivity (Λm) is defined by the relation Λm = κ/c, where c is the concentration. It can also be expressed as Λm = (κ × 1000)/c with units of S cm² mol⁻¹.
Conductivity always decreases with decrease in concentration for both weak and strong electrolytes. This is because the number of ions per unit volume that carry the current in a solution decreases on dilution, reducing the overall conductance.
Molar conductivity increases with decrease in concentration. For strong electrolytes, the increase is gradual with dilution. However, for weak electrolytes, the increase is very steep in dilute solutions due to increased degree of dissociation.
Explanation
The answer covers both definitions and the variation with concentration as asked in the question. The definitions are taken directly from the textbook context, and the variation explanation distinguishes between strong and weak electrolytes. The word count (approximately 110 words) is appropriate for a 3-mark question.