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

Options

A. `Li^(+) gt Na^(+) gt K^(+) gt Rb^(+)`
B. `Na^(+) gt K^(+) gt Rb^(+) gt Li^+`
C. `K^(+) gt Rb^(+) gt Na^(+) gt Li^(+)`
D. `Rb^(+) gt K^(+) gt Na^(+) gt Li^(+)`

Answer

D

Explanation

The correct order of the mobility of the alkali metal ions in aqueous solution is `Rb^(+) gt K^(+) gt Na^(+) gt Li^(+)` due to following order of hydration energy of these ions `Li^(+) gt Na^(+) gt K^+ gt Rb^+` and as the hydration of ion increases, mobility decreases.
Hydration enthalpy `prop 1/"Size of cation"`