Question

Which among the following metal ions has the highest enthalpy of hydration? (Assume the given metal ions have the same counter ion.) Given: Atomic numbers of Ti, V, Cr and Mn are 22, 23, 24 and 25, respectively.

• A. Ti\(^{2+}\)
• B. V\(^{2+}\)
• C. Cr\(^{2+}\)
• D. Mn\(^{2+}\)

Hint:

Smaller metal ions with higher charges have higher enthalpies of hydration due to their greater charge density, which attracts water molecules more strongly.

Answer 1

The Correct Option is B

Step 1: Understanding Enthalpy of Hydration.
The enthalpy of hydration refers to the energy released when an ion is dissolved in water and surrounded by water molecules. Smaller ions with higher charges tend to have a higher enthalpy of hydration because they can attract water molecules more strongly.
Step 2: Comparing the Options.
- (A) Ti\(^{2+}\): Titanium has a relatively higher atomic number, which results in a smaller ionic radius, but not as small as V\(^{2+}\).
- (B) V\(^{2+}\): Vanadium has a relatively smaller ionic radius than the other ions listed, meaning it can have a higher enthalpy of hydration. This is the correct answer.
- (C) Cr\(^{2+}\): Chromium has a slightly larger ionic radius compared to V\(^{2+}\), so its enthalpy of hydration is lower.
- (D) Mn\(^{2+}\): Manganese has a larger ionic radius than V\(^{2+}\), meaning its enthalpy of hydration is lower compared to V\(^{2+}\).
Step 3: Conclusion.
The correct answer is (B) V\(^{2+}\), as it has the highest enthalpy of hydration due to its smaller ionic radius and higher charge density.