Question

Assertion (A): The stability of Cu\(^ {2+}\) ions is less than Cu\(^+\) in their aqueous solution.
Reason (R): Aqueous Cu\(^ {2+}\) has more negative \(\Delta_{hyd}H^0\) than Cu\(^+\).

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A).
• C. (A) is correct but (R) is incorrect.
• D. (A) is incorrect but (R) is correct.

Hint:

Always compare hydration enthalpies with ionic charge and size to determine the stability of ions in aqueous solution. Cu\(^{2+}\) is generally more stable than Cu\(^{+}\) due to higher charge density, even if the assertion claims otherwise.

Answer 1

The Correct Option is D

Step 1: Evaluating the assertion.
The claim that Cu²⁺ is less stable than Cu⁺ in aqueous solution is false; Cu²⁺ is actually more stable due to stronger hydration from its higher charge density.

Step 2: Evaluating the reason.
Hydration enthalpy (Δ_hyd H°) is more negative for Cu²⁺ than Cu⁺ because of greater charge and smaller radius, making this statement true.

Step 3: Connecting assertion and reason.
The true reason contradicts the assertion rather than supporting it, so it does not serve as a correct explanation.

Step 4: Final conclusion.
Assertion (A) is incorrect, but Reason (R) is correct.