Question

The stability of \(Cu^{2+}\) is more than \(Cu^+\) salts in aqueous solution due to

• A. Enthalpy of atomization
• B. Hydration energy
• C. Second ionisation enthalpy
• D. First ionisation enthalpy

Answer 1

The Correct Option is B

In aqueous solutions, the stability of \(Cu^{2+}\) compared to \(Cu^+\) salts is primarily due to the differences in their hydration energy. Let's explore this concept: 

Hydration Energy: When ions dissolve in water, they become surrounded by water molecules. This interaction releases energy, known as hydration energy. The magnitude of hydration energy depends on the charge density of the ion; higher charges and smaller radii lead to higher hydration energies.

Comparison of \(^+\) and \((Cu^{2+}\):

• \(Cu^{2+}\): Higher charge (+2) results in a significantly stronger attraction to water molecules, leading to a higher hydration energy.
• \(Cu^+\): Lower charge (+1) results in a weaker attraction, yielding lower hydration energy.

Due to the greater hydration energy of \(Cu^{2+}\), it is more stable than \(Cu^+\) in aqueous solutions. This enhanced stability favors the presence of \(Cu^{2+}\) over \(Cu^+\) in solution, explaining why hydration energy is the key factor in determining the stability.

Answer 2

\(Cu_{(s)} \to Cu_{(g)} \to Cu_{(g)}^+   \to   Cu_{(g)}^{2+}   \to  Cu_{(aq)}^{2+}\)
Because \(Cu^{2+}\) releases more hydration energy than \(Cu^+\), it is more stable than the latter.
Therefore, The correct option is (B): Hydration energy