The cell reaction `Cr_2O_7^(2-)(aq)+14H^+(aq)+6Fe^(2+)(aq)to6Fe^(3+)(aq)+2Cr^(3+)(aq)+7H_2O(l)` is best represented by:

Options

A. `Pt(s)|Fe^(2+)(aq),Fe^(3+)(aq)"||"Cr_2O_7^(2-)(aq),Cr^(3+)(aq)|Pt(s)`
B. `Pt(s)|Cr_2O_7^(2-)(aq),Cr^(+3)(aq)"||"Fe^(3+)(aq),Fe^(+2)(aq)|Pt(s)`
C. `Fe^(2+)(aq)|Fe^(3+)(aq)"||"Cr_2O_7^(2-)(aq)|Cr^(3+)(aq)`
D. `Cr_2O_7^(2-)(aq)|Cr^(3+)(aq)"||"Fe^(3+)(aq)|Fe^(2+)(aq)`

Answer

To represent the given cell reaction correctly, we need to follow the standard format for writing electrochemical cell representations. Here’s a step-by-step solution:

### Step 1: Identify the Anodic and Cathodic Reactions
- **Anodic Reaction (Oxidation)**: In the given reaction, Fe²⁺ is oxidized to Fe³⁺. The half-reaction can be written as:
\[ \text{Oxidation: } \text{Fe}^{2+} \rightarrow \text{Fe}^{3+} + e^- \]
- **Cathodic Reaction (Reduction)**: Cr₂O₇²⁻ is reduced to Cr³⁺. The half-reaction can be written as:
\[ \text{Reduction: } \text{Cr}_2\text{O}_7^{2-} + 14\text{H}^+ + 6e^- \rightarrow 2\text{Cr}^{3+} + 7\text{H}_2\text{O} \]

### Step 2: Write the Overall Cell Reaction
The overall cell reaction combines both half-reactions:
\[ \text{Cr}_2\text{O}_7^{2-} + 14\text{H}^+ + 6\text{Fe}^{2+} \rightarrow 6\text{Fe}^{3+} + 2\text{Cr}^{3+} + 7\text{H}_2\text{O} \]

### Step 3: Identify the Inert Electrode
Since the half-reactions involve ions in solution, we need an inert electrode to facilitate the electron transfer. Platinum (Pt) is commonly used as an inert electrode.

### Step 4: Write the Cell Representation
The standard format for cell representation is:
\[ \text{Anode (Oxidation)} \, | \, \text{Salt Bridge} \, | \, \text{Cathode (Reduction)} \]
Thus, the cell representation will be:
\[ \text{Pt (s)} | \text{Fe}^{2+} (aq), \text{Fe}^{3+} (aq) \, || \, \text{Cr}_2\text{O}_7^{2-} (aq), \text{H}^+ (aq) | \text{Cr}^{3+} (aq) \, | \text{Pt (s)} \]

### Final Cell Representation
Putting it all together, the best representation of the cell reaction is:
\[ \text{Pt (s)} | \text{Fe}^{2+} (aq), \text{Fe}^{3+} (aq) \, || \, \text{Cr}_2\text{O}_7^{2-} (aq), \text{H}^+ (aq) | \text{Cr}^{3+} (aq) \, | \text{Pt (s)} \]