Question

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

• A. $L{i}^{+}>N{a}^{+}>K^{+}>R{b}^{+}$
• B. $N{a}^{+}>K^{+}>R{b}^{+}>L{i}^{+}$
• C. $K^{+}>R{b}^{+}>N{a}^{+}>L{i}^{+}$
• D. $R{b}^{+}>K^{+}>N{a}^{+}>L{i}^{+}$

Answer 1

Answer: (D)

$R{b}^{+}>K^{+}>N{a}^{+}>L{i}^{+}$

In case of aqueous solution, hydration of cation occurs

$Hydration\propto \frac{1}{size}\propto Z_{eff}$

Smaller the cation higher will be hydration, which results in increase in effective size (solvation sphere), hence mobility decreases.

${Rb}^{+}>K^{+}>{Na}^{+}>{Li}^{+}$