For the cell prepared from electrode A and B, electrode A:`(Cr_2O_7^(2-))/(Cr^(3+)), E_("red")^(0)=+1.33V` and electrode B :`(Fe^(3+))/(Fe^(2+)), E_("red")^(0)=0.77 V`, which of the following statement is not correct ?

Options

A. The electrons will flow B to A (in the outer circuit) when connections are made.
B. The standard e.m.f. of the cell with be 0.56 V
C. A will be positive electrode
D. None of the above

Explanation

To solve the problem, we need to analyze the given electrochemical cell with two electrodes, A and B, and their respective reduction potentials.

### Step 1: Identify the electrodes and their reduction potentials
- **Electrode A**: \( \text{Cr}_2\text{O}_7^{2-}/\text{Cr}^{3+} \), \( E^\circ_{\text{red}} = +1.33 \, \text{V} \)
- **Electrode B**: \( \text{Fe}^{3+}/\text{Fe}^{2+} \), \( E^\circ_{\text{red}} = +0.77 \, \text{V} \)

### Step 2: Determine which electrode acts as the anode and which as the cathode
- The electrode with the higher reduction potential acts as the cathode (where reduction occurs), and the one with the lower reduction potential acts as the anode (where oxidation occurs).
- Here, Electrode A has a higher reduction potential (+1.33 V) than Electrode B (+0.77 V). Therefore:
- **Anode**: Electrode B (Fe3+/Fe2+)
- **Cathode**: Electrode A (Cr2O7^{2-}/Cr^{3+})

### Step 3: Determine the direction of electron flow
- Electrons flow from the anode to the cathode. Therefore, electrons will flow from Electrode B (anode) to Electrode A (cathode).

### Step 4: Calculate the standard EMF of the cell
- The standard EMF (E°cell) can be calculated using the formula:
\[ E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}} \]
- Substituting the values:
\[ E^\circ_{\text{cell}} = 1.33 \, \text{V} - 0.77 \, \text{V} = 0.56 \, \text{V} \]

### Step 5: Analyze the statements provided in the question
1. **Statement 1**: Electrons will flow from B to A in the outer circuit when connections are made. (True)
2. **Statement 2**: The standard EMF of the cell will be 0.56 volts. (True)
3. **Statement 3**: A will be a positive electrode. (True, since A is the cathode)
4. **Statement 4**: None of the above. (This implies all previous statements are correct)

### Conclusion
Since all the statements are correct, the statement that is not correct is **Statement 4**: "None of the above."

### Final Answer
The statement that is not correct is **Statement 4**: None of the above.

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