Question

Both Cr²⁺ and Mn³⁺ have d⁴ configuration. Which one of the following is true?

• A. Mn³⁺ is a reducing agent but Cr²⁺ is an oxidising agent
• B. Mn³⁺ is a oxidising agent but Cr²⁺ is an reducing agent
• C. Both Mn³⁺ and Cr²⁺ are oxidising agents
• D. Both Mn³⁺ and Cr²⁺ are reduncing agents
• E. Both Mn³⁺ and Cr²⁺ are neither reducing nor oxidising agents

Answer 1

The Correct Option is B

In this question, we are asked to determine the oxidation states of Mn and Cr in their respective ions and their ability to act as reducing or oxidising agents. Both Mn\(^{3+}\) and Cr\(^{2+}\) have a d\(^4\) configuration. Mn\(^{3+}\) has a higher oxidation state compared to Mn\(^{2+}\), making it an oxidising agent as it is capable of accepting electrons and being reduced to Mn\(^{2+}\). On the other hand, Cr\(^{2+}\) has a lower oxidation state compared to Cr\(^{3+}\), making it a reducing agent as it is capable of donating electrons and being oxidised to Cr\(^{3+}\).

The correct option is (B) : Mn³⁺ is a oxidising agent but Cr²⁺ is an reducing agent

Answer 2

The correct answer is Mn³⁺ is an oxidising agent but Cr²⁺ is a reducing agent.

Explanation:

• Mn³⁺ (d⁴): In the case of Mn³⁺, the ion has a relatively high oxidation state. It can readily gain an electron to reduce to Mn²⁺ (d⁵), which is a more stable state due to the half-filled d-orbital. Thus, Mn³⁺ acts as an oxidising agent, as it has the tendency to accept electrons and get reduced.
• Cr²⁺ (d⁴): For Cr²⁺, this ion has a lower oxidation state and is more prone to lose electrons to reach the more stable Cr³⁺ (d³) state. Thus, Cr²⁺ behaves as a reducing agent, as it has the tendency to donate electrons and get oxidised.

Conclusion: Mn³⁺ is an oxidising agent and Cr²⁺ is a reducing agent, making the correct statement:

Mn³⁺ is an oxidising agent but Cr²⁺ is a reducing agent.