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: Understanding the assertion (A).
The statement claims that Cu\(^ {2+}\) ions are less stable than Cu\(^+\) in aqueous solution. In reality, Cu\(^ {2+}\) is more stable than Cu\(^+\) in aqueous solution due to its higher charge density and stronger hydration, which leads to a more negative hydration enthalpy. Hence, the assertion is incorrect.

Step 2: Understanding the reason (R).
Hydration enthalpy (\(\Delta_{hyd} H^0\)) represents the energy released when gaseous ions are solvated by water molecules. Cu\(^ {2+}\) has a higher positive charge than Cu\(^+\) and a smaller ionic radius, resulting in a stronger attraction to water molecules and therefore a more negative \(\Delta_{hyd} H^0\). This statement is correct.

Step 3: Relation between (A) and (R).
Although (R) is true, it does not support the claim in (A). A more negative hydration enthalpy indicates higher stability of Cu\(^ {2+}\), contradicting the assertion that Cu\(^ {2+}\) is less stable. Therefore, (R) is correct, but it is not the correct explanation for (A).

Step 4: Final conclusion.
- Assertion (A): Incorrect.
- Reason (R): Correct, but does not explain (A).
\[ \boxed{\text{Answer: (A) is incorrect but (R) is correct.}} \]