Ionic mobility of which of the following alkali metal ions is lowest when aqueous solution of their salts are put under an electric field ?

Options

A. K
B. Rb
C. Li
D. Na

Answer

C

Explanation

Ionic mobility `prop 1/("size of hydrated ion")`
Smaller size hydrated ion in aq. Solution `-Rb^(+) (aq)`
Larger size hydrated ion in aq. Solution `Li^(+) (aq)`
Lowest ionic mobility in aq. Solution `to Li^(+) (aq)` due to high hydration