Which of the following reaction is spontaneous oxidation - reduction reaction

Options

A. `Mn^(+2)+5Fe^(+3)+4H_(2)OrarrMnO_(4)^(-)+5Fe^(+2)+8H^(+)`
B. `MnO_(4)^(-)+5Fe^(+3)+8H^(+)rarrMn^(+2)+5Fe^(+2)+4H_(2)O`
C. `MnO_(4)^(-)+5Fe^(+2)+8H^(+)rarrMn^(+2)+5Fe^(+3)+4H_(2)O`
D. `Mn^(+2)+5Fe^(+2)+4H_(2)OrarrMnO_(4)^(-)+5Fe^(+3)+8H^(+)`

Answer

To determine which of the given reactions is a spontaneous oxidation-reduction (redox) reaction, we need to analyze each option based on the oxidation states of the elements involved and the direction of the reaction.

### Step-by-Step Solution:

1. **Understanding Redox Reactions**:
- A redox reaction involves the transfer of electrons between two species. One species gets oxidized (loses electrons) and the other gets reduced (gains electrons).

2. **Identifying Oxidation States**:
- For each option, identify the oxidation states of the elements involved in the reaction.

3. **Analyzing Option A**:
- The reaction involves Mn²⁺ converting to MnO₄⁻.
- Mn²⁺ has an oxidation state of +2, while MnO₄⁻ has an oxidation state of +7.
- This means Mn is being oxidized from +2 to +7, which is not spontaneous as Mn prefers to be in a lower oxidation state (+2 is more stable than +7).
- **Conclusion**: Option A is not a spontaneous redox reaction.

4. **Analyzing Option B**:
- This option is not provided in the transcript, but you would follow the same method: determine the oxidation states and check if there is a spontaneous electron transfer.

5. **Analyzing Option C**:
- In this option, we have Mn being reduced from +7 (in MnO₄⁻) to +2 (in Mn²⁺) and Fe being reduced from +3 (in Fe³⁺) to +2 (in Fe²⁺).
- Here, Mn is acting as an oxidizing agent (it is reduced), and Fe is the reducing agent (it is oxidized).
- This reaction is spontaneous because Mn can readily accept electrons to go from +7 to +2, while Fe can easily lose electrons to go from +3 to +2.
- **Conclusion**: Option C is a spontaneous redox reaction.

6. **Analyzing Option D**:
- Similar to Option A, if it involves Mn going from +7 to +2 in reverse, it is not spontaneous.
- **Conclusion**: Option D is not a spontaneous redox reaction.

7. **Final Conclusion**:
- Based on the analysis, the only spontaneous oxidation-reduction reaction is found in Option C.

### Final Answer:
The correct answer is **Option C**.

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