Using the standard electrode potential, find out the pair between which redox reaction is not feasible.
`E^(θ)` values: `Fe^(3+)//Fe^(2+)=0.77, I_(2)//I^(-)=+0.54`,
`Cu^(2+)//Cu=+0.34, Ag^(+)//Ag=+0.80V`

Options

A. `Fe^(3+)` and `I^(-)`
B. `Ag^(+)` and `Cu`
C. `Fe^(3+)` and `Cu`
D. `Ag` and `Fe^(3+)`

Explanation

To determine which redox reaction is not feasible using the standard electrode potentials, we will analyze each pair of half-reactions provided. The feasibility of a redox reaction can be determined by calculating the standard cell potential (E°cell) using the formula:

\[ E°_{cell} = E°_{reduction} - E°_{oxidation} \]

If the calculated E°cell is positive, the reaction is feasible; if it is negative, the reaction is not feasible.

### Step-by-Step Solution:

1. **Identify the Half-Reactions and Their Standard Potentials:**
- For each pair, identify the reduction and oxidation half-reactions and their corresponding standard electrode potentials (E°).

2. **Calculate E°cell for Each Pair:**
- **Pair 1: Fe³⁺/Fe²⁺ and I₂/I⁻**
- Reduction: \( \text{Fe}^{3+} + 2e^- \rightarrow \text{Fe}^{2+} \) (E° = +0.77 V)
- Oxidation: \( \text{I}^- \rightarrow \text{I}_2 + 2e^- \) (E° = -0.54 V, since we reverse the reaction)
- E°cell = +0.77 V - (-0.54 V) = +0.77 V + 0.54 V = +0.23 V (Feasible)

- **Pair 2: Ag⁺/Ag and Cu²⁺/Cu**
- Reduction: \( \text{Ag}^+ + e^- \rightarrow \text{Ag} \) (E° = +0.80 V)
- Oxidation: \( \text{Cu} \rightarrow \text{Cu}^{2+} + 2e^- \) (E° = -0.34 V, since we reverse the reaction)
- E°cell = +0.80 V - (-0.34 V) = +0.80 V + 0.34 V = +0.46 V (Feasible)

- **Pair 3: Fe³⁺/Fe²⁺ and Cu²⁺/Cu**
- Reduction: \( \text{Fe}^{3+} + 2e^- \rightarrow \text{Fe}^{2+} \) (E° = +0.77 V)
- Oxidation: \( \text{Cu} \rightarrow \text{Cu}^{2+} + 2e^- \) (E° = -0.34 V)
- E°cell = +0.77 V - (-0.34 V) = +0.77 V + 0.34 V = +0.43 V (Feasible)

- **Pair 4: Ag⁺/Ag and Fe³⁺/Fe²⁺**
- Reduction: \( \text{Fe}^{3+} + 2e^- \rightarrow \text{Fe}^{2+} \) (E° = +0.77 V)
- Oxidation: \( \text{Ag} \rightarrow \text{Ag}^+ + e^- \) (E° = -0.80 V, since we reverse the reaction)
- E°cell = +0.77 V - (-0.80 V) = +0.77 V + 0.80 V = -0.03 V (Not Feasible)

3. **Conclusion:**
- The pair between which the redox reaction is not feasible is **Ag⁺/Ag and Fe³⁺/Fe²⁺**.

### Final Answer:
The redox reaction between **Ag⁺/Ag and Fe³⁺/Fe²⁺** is not feasible.