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 Ki^(+) `

Answer

D

Explanation

Key idea Mobility of alkali ions in aqueous solution `prop` size of ion
`prop (1)/("size of hydrated ion")`
The mobility of alkali ions is inversely proportional to the size of ion in hydrated state, because smaller the ion more it will get hydrated and becomes larger in size, thus its ionic mobility decreases.
Hence correct order of mobility is
`Rb^(+) gt K^(+) gt Na^(+) gt Li^(+)`