QuestionElectrochemistry / ionic mobility
What will be the correct order of mobility of the following alkali metal ions in aqueous solution?
- (a) Li⁺ > Na⁺ > K⁺ > Rb⁺
- (b) Na⁺ > K⁺ > Rb⁺ > Li⁺
- (c) K⁺ > Rb⁺ > Na⁺ > Li⁺
- (d) Rb⁺ > K⁺ > Na⁺ > Li⁺
Answer: (d) Rb⁺ > K⁺ > Na⁺ > Li⁺
Smaller ions are more hydrated: Li⁺ drags the largest water shell, so moves slowest. Mobility: Rb⁺ > K⁺ > Na⁺ > Li⁺ → (d). Remember: hydrated size order is the reverse of crystal size.