Question

Which is the strongest oxidising agent among: \[ Cr^{3+}, \; V^{3+}, \; Mn^{3+} \]

Hint:

Half-filled and fully filled d-configurations are especially stable.

Answer 1

Which is the strongest oxidising agent among Cr\(^{3+}\), V\(^{3+}\), and Mn\(^{3+}\)?
To determine which ion is the strongest oxidising agent, we need to consider the standard reduction potentials (E°) of the half-reactions involving these ions. A stronger oxidising agent corresponds to a more positive reduction potential.

The reduction half-reactions and their standard electrode potentials are as follows:
1. For Chromium (Cr\(^{3+}\)): \[ \text{Cr}^{3+} + 3e^- \rightarrow \text{Cr} \quad E^\circ = -0.74\,V \] 2. For Vanadium (V\(^{3+}\)): \[ \text{V}^{3+} + 3e^- \rightarrow \text{V} \quad E^\circ = -0.26\,V \] 3. For Manganese (Mn\(^{3+}\)): \[ \text{Mn}^{3+} + e^- \rightarrow \text{Mn}^{2+} \quad E^\circ = +1.51\,V \] Step 1: Understanding Oxidising Agent Strength
An oxidising agent is a species that gains electrons (is reduced) in a chemical reaction. The stronger the oxidising agent, the more easily it will accept electrons.

Step 2: Compare Reduction Potentials
- Cr\(^{3+}\) has a reduction potential of \( -0.74\,V \). - V\(^{3+}\) has a reduction potential of \( -0.26\,V \). - Mn\(^{3+}\) has a reduction potential of \( +1.51\,V \).

Conclusion:
Mn\(^{3+}\) is the strongest oxidising agent among Cr\(^{3+}\), V\(^{3+}\), and Mn\(^{3+}\) because it has the most positive reduction potential of \( +1.51\,V \), indicating it is most easily reduced. The more positive the reduction potential, the stronger the oxidising agent.