Question

Assertion :The mobility of sodium ion is lower than that of potassium ion. Reason: The ionic mobilities depend on the effective radius of the ion.

Read the above assertion and reason and choose the correct option regarding it.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Smaller cation, larger hydration thus smaller molar ionic conductance.

Ionic size : $L{i}^{+}<N{a}^{+}<K^{+}<R{b}^{+}$

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

Size of hydration ion : $L{i}^{+}>N{a}^{+}>K^{+}>R{b}^{+}$

Molar ionic conductance : $L{i}^{+}<N{a}^{+}<K^{+}<R{b}^{+}$

As we go down the group, ions are easily moveable so conductivity increases.