Question

Choose the correct order of molar ionic conductivities of the following ions.

• A. \( \text{Li}^+ < \text{Na}^+ < \text{K}^+ < \text{Rb}^+ \)
• B. \( \text{Li}^+ < \text{K}^+ < \text{Rb}^+ < \text{Na}^+ \)
• C. \( \text{Li}^+ < \text{Na}^+ < \text{Rb}^+ < \text{K}^+ \)
• D. \( \text{Li}^+ < \text{Rb}^+ < \text{Na}^+ < \text{K}^+ \)

Hint:

Molar ionic conductivity increases with the size of the ion in a given group, as larger ions experience less friction in solution.

Answer 1

The Correct Option is A

Step 1: Understanding Molar Ionic Conductivity
The molar ionic conductivity of an ion is influenced by its size and the ability to move through the solvent.
As the size of the ion increases, the molar ionic conductivity typically increases because larger ions experience less friction in solution.
Step 2: Explanation of the Trend
\( \text{Li}^+ \) is the smallest ion in the group, so it has the lowest molar ionic conductivity.

\( \text{Na}^+ \) is larger than \( \text{Li}^+ \) and has a higher molar ionic conductivity.

\( \text{K}^+ \) is larger than \( \text{Na}^+ \), so its molar ionic conductivity is higher.
\( \text{Rb}^+ \) is the largest ion in the group, so it has the highest molar ionic conductivity.

Step 3: Conclusion
Thus, the correct order of molar ionic conductivities is \( \text{Li}^+ < \text{Na}^+ < \text{K}^+ < \text{Rb}^+ \).