The `E^(@)` value in respect of the electrodes chromium `(Z=24)`, manganese `(Z=25)` and iron `(Z=26)` are : `Cr^(3+)//Cr^(2+)=-0.4V,Mn^(3+)//Mn^(2+)=+1.5V`, " " `Fe^(3+)//Fe^(2)=+0.8V`.
On the basic of the above information compare the feasibilities
of further oxidation of their `+2` oxidation states.

Answer

To compare the feasibilities of further oxidation of the +2 oxidation states of chromium (Cr), manganese (Mn), and iron (Fe), we can analyze the given standard electrode potentials (E° values) and the electronic configurations of the ions involved.

### Step-by-Step Solution:

1. **Identify the Given E° Values:**
- For Chromium: \( \text{Cr}^{3+} + e^- \rightarrow \text{Cr}^{2+} \) with \( E° = -0.4 \, V \)
- For Manganese: \( \text{Mn}^{3+} + e^- \rightarrow \text{Mn}^{2+} \) with \( E° = +1.5 \, V \)
- For Iron: \( \text{Fe}^{3+} + e^- \rightarrow \text{Fe}^{2+} \) with \( E° = +0.8 \, V \)

2. **Understand the Implications of E° Values:**
- A more positive E° value indicates a greater tendency to gain electrons (i.e., a stronger oxidizing agent).
- Conversely, a negative E° value indicates a lesser tendency to gain electrons (i.e., a weaker oxidizing agent).

3. **Analyze the Stability of +2 Oxidation States:**
- **Chromium (Cr):**
- \( \text{Cr}^{2+} \) has a configuration of \( 3d^4 \).
- \( \text{Cr}^{3+} \) has a configuration of \( 3d^3 \), which is exceptionally stable due to its half-filled T2G subshell.
- Since \( E° \) is negative, \( \text{Cr}^{2+} \) is less stable and has a low tendency to oxidize to \( \text{Cr}^{3+} \).

- **Manganese (Mn):**
- \( \text{Mn}^{2+} \) has a configuration of \( 3d^5 \).
- \( \text{Mn}^{3+} \) has a configuration of \( 3d^4 \), which is less stable than \( 3d^5 \) (half-filled).
- The positive \( E° \) value indicates that \( \text{Mn}^{2+} \) is stable and has a high tendency to oxidize to \( \text{Mn}^{3+} \).

- **Iron (Fe):**
- \( \text{Fe}^{2+} \) has a configuration of \( 3d^6 \).
- \( \text{Fe}^{3+} \) has a configuration of \( 3d^5 \), which is stable due to half-filling.
- The positive \( E° \) value indicates that \( \text{Fe}^{2+} \) is stable but less so than \( \text{Mn}^{2+} \) and has a moderate tendency to oxidize to \( \text{Fe}^{3+} \).

4. **Compare the Stability and Feasibility of Oxidation:**
- **Most Stable +2 State:** \( \text{Mn}^{2+} \) (due to half-filled d-subshell)
- **Moderately Stable +2 State:** \( \text{Fe}^{2+} \) (stable but less than Mn)
- **Least Stable +2 State:** \( \text{Cr}^{2+} \) (due to negative E° value)

5. **Conclusion:**
- The feasibility of further oxidation of their +2 oxidation states is as follows:
- \( \text{Mn}^{2+} \) can easily oxidize to \( \text{Mn}^{3+} \).
- \( \text{Fe}^{2+} \) can oxidize to \( \text{Fe}^{3+} \) but is less favorable than Mn.
- \( \text{Cr}^{2+} \) is the least likely to oxidize to \( \text{Cr}^{3+} \) due to its negative E° value.