Question

An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to

• A. increase in number of ions
• B. increase in the ionic mobility of ions
• C. 100% ionisation of the electrolyte at normal dilution
• D. increase in both i.e., number of ions and ionic mobility of ions

Answer 1

The Correct Option is B

The question asks why the equivalent conductance of a strong electrolyte increases with dilution. Let's explore the concept step-by-step to understand the correct reasoning:

1. Understanding Equivalent Conductance: Equivalent conductance \(\Lambda_{\text{eq}}\) of an electrolyte provides a measure of its ability to conduct electricity when dissolved in a solution. It is calculated as the conductivity \(\kappa\) of the solution divided by the concentration \(C\), expressed in terms of gram equivalents per liter: \(\Lambda_{\text{eq}} = \frac{\kappa}{C}\).
2. Conductance and Dilution: As a strong electrolyte is diluted, the number of ions per unit volume that can potentially carry charge remains high because strong electrolytes are almost completely ionized in solution. However, the key factor here is the ionic mobility.
3. Ionic Mobility: Dilution results in decreased interionic attractions, allowing ions to move more freely. The additional space enables higher mobility of ions, contributing to increased equivalent conductance.
4. Other Factors: While the number of ions per unit volume effectively decreases with dilution, it does not increase. Thus, the primary reason for increased conductance is not an increase in the number of ions.
5. Conclusion: The increase in equivalent conductance with dilution is mainly due to the increase in the ionic mobility of ions rather than an increase in the number of ions.

Therefore, the correct answer is that the increase in equivalent conductance with dilution is mainly due to an increase in the ionic mobility of ions.