Question

For a given concentration, the ionic conductance in water is of the order:

• A. Li⁺> Na⁺ >K⁺ >Rb⁺
• B. Li⁺< Na⁺ <K⁺ <Rb⁺
• C. Na⁺<K⁺ <Rb⁺<Li⁺
• D. All ions will exhibit equalconductance

Answer 1

The correct option is B

Li⁺< Na⁺ <K⁺ <Rb⁺

$L{i}^{+}$ is the smallest of the given ions and owing to this size, it is the most polarizing of these ions. Charge per ionic volume is the highest for $L{i}^{+}$ ion and thus the degree of hydration will be the highest.

The greater the degree of hydration, the higher will be the hydration enthalpy. This means that the solvated ionic radius will be the largest for $L{i}^{+}$ in water. With the largest (of the given) solvated ionic radius, $L{i}^{+}$ ions will be the bulkiest and thus will exhibit least the conductance.