Step 1 (Governing Principles): [1 Mark]

• Conductivity ($\kappa$): Defined as the conductance of a unit volume of solution. It depends on the number of ions per unit volume.
• Molar Conductivity ($\Lambda_m$): Defined as the conducting power of all the ions produced by one mole of an electrolyte in a given volume $V$ of solution. It is related to conductivity by the formula: $$\Lambda_m = \frac{\kappa \times 1000}{C}$$ where $C$ is the molar concentration.

Step 2 (Step-by-Step Reasoning): [0.5 Mark]

• Variation of Conductivity ($\kappa$): As the concentration of the solution decreases (dilution), the number of ions per unit volume decreases. Consequently, the conductivity ($\kappa$) decreases for both strong and weak electrolytes.
• Variation of Molar Conductivity ($\Lambda_m$): As the concentration decreases, the total volume $V$ containing one mole of electrolyte increases significantly. Although $\kappa$ decreases, the increase in volume $V$ dominates, leading to an overall increase in $\Lambda_m$.

Step 3 (Final Concluded Answer): [0.5 Mark]

• Conclusion: Conductivity ($\kappa$) decreases with dilution due to a decrease in the number of ions per unit volume. Molar conductivity ($\Lambda_m$) increases with dilution because the increase in the volume of the solution containing one mole of electrolyte outweighs the decrease in conductivity.

💡 EL10 Concept Insight: Imagine a crowded room (high concentration); conductivity is like how many people can walk through a door at once. If you spread those same people out into a massive stadium (dilution), there are fewer people near the door (lower conductivity), but because you have so much more space to move around in, the total "power" of that group to move across the area increases (higher molar conductivity).