Question

The correct order of the mobility of the alkali metal ions in aqueous solution is

• A. $ Li^+ > Na^+ > K^+ > Rb^+ $
• B. $ Na^+ > K^+ > Rb^+ > Li^+ $
• C. $ K^+ > Rb^+ > Na^+ > Li^+ $
• D. $ Rb^+ > K^+ > Na^+ > Li^+ $

Answer 1

The Correct Option is D

The given question requires us to determine the correct order of mobility of alkali metal ions in an aqueous solution. The options provided are based on the mobility of different alkali metal ions: Li^+, Na^+, K^+, and Rb^+.

Alkali metal ions in aqueous solutions have different mobilities due to the hydration effect. In aqueous solution, these ions are surrounded by water molecules, and the ease of movement depends on the size of the hydration shell around them.

Here is the step-by-step explanation:

1. The mobility of ions in solution depends on their ion size and the extent to which they are hydrated. Smaller ions tend to be more highly hydrated, which affects their mobility.
2. Li^+ being the smallest has the largest hydration shell, which makes it move more sluggishly compared to larger ions.
3. Na^+, K^+, and Rb^+ have decreasing levels of hydration as we move from Na^+ to Rb^+ because their ionic radii increase.
4. Since Rb^+ has the least hydration due to its larger size compared to the others, it exhibits the greatest mobility in an aqueous solution.

Therefore, based on the above reasoning, the mobility of alkali metal ions in aqueous solution follows the order: Rb^+ > K^+ > Na^+ > Li^+. Hence, the correct answer is:

Rb^+ > K^+ > Na^+ > Li^+

This order is justified because larger ions with less hydration are able to move more freely through the solution.