Question

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

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

Answer 1

The correct option is D $Li$

$L{i}^{+}$ ion being smallest, has the maximum charge density.
$\therefore L{i}^{+}$ is most heavily hydrated among all alkali metal ions. The effective size of $L{i}^{+}$ in aqueous solution is therefore, largest.
$\therefore$ $L{i}^{+}$ moves the slowest under the influence of an electric field.