Question

Assertion Among the alkali metals, lithium salts exhibit the least electrical conductance in aqueous solutions.
Reason Smaller the radius of the hydrated cation, lower is the electrical conductance in aqueous solutions.

• A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion
• B. If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion
• C. If Assertion is true but Reason is false
• D. If both Assertion and Reason are false

Answer 1

Answer: (C)

Hydration energy varies inversely with size. Hence, as we move from $Li$ to $Cs$, size of alkali metals increases and thus, hydration energy
decreases. Thus, lithium ion being smallest in size among alkali metals, is most extensively hydrated and becomes largest in size. Thus, it has least electrical conductivity among alkali metals.
Electrical conductance $\propto \frac{1}{\text{ size of hydrated cation }}$