Which of the following reactions is `//` are possible at the anode ?

Options

A. `F_(2)+2e^(-) rarr 2F^(c-)`
B. `2H^(o+)+(1)/(2)O(2) +2e^(-) rarr H_(2)O`
C. .2
C
r
3
+
+
7
H
2
O
→
C
r
2
O
2
−
7
+
14
H
⊕
+
6
e
−
`
D. `Fe^(2+) rarr Fe^(3+)+e^(-)`

Explanation

To determine which reactions are possible at the anode, we need to understand that oxidation occurs at the anode during electrochemical reactions. Let's analyze each reaction step by step.

### Step-by-Step Solution:

1. **Identify the Reactions:**
- Reaction 1: Fluorine gas (F₂) is reduced to fluoride ions (F⁻).
- Reaction 2: Hydrogen ions (H⁺) are reduced to water (H₂O).
- Reaction 3: Chromium ions (Cr³⁺) and water are oxidized to dichromate ions (Cr₂O₇²⁻) and hydrogen ions (H⁺).
- Reaction 4: Ferrous ions (Fe²⁺) are oxidized to ferric ions (Fe³⁺).

2. **Determine the Nature of Each Reaction:**
- **Reaction 1:** This is a reduction reaction (F₂ → 2F⁻), as fluorine is gaining electrons. Therefore, it cannot occur at the anode.
- **Reaction 2:** This is also a reduction reaction (2H⁺ + 2e⁻ → H₂O), as hydrogen ions are gaining electrons. Therefore, it cannot occur at the anode.
- **Reaction 3:** This reaction involves the oxidation of chromium ions (2Cr³⁺ + 7H₂O → Cr₂O₇²⁻ + 14H⁺ + 6e⁻). Here, the oxidation state of chromium increases from +3 to +6, indicating that it is losing electrons. Therefore, this reaction can occur at the anode.
- **Reaction 4:** This reaction involves the oxidation of ferrous ions (Fe²⁺ → Fe³⁺ + e⁻). The ferrous ions are losing electrons, indicating that this reaction can also occur at the anode.

3. **Conclusion:**
- The reactions that can occur at the anode are:
- Reaction 3 (oxidation of Cr³⁺ to Cr₂O₇²⁻)
- Reaction 4 (oxidation of Fe²⁺ to Fe³⁺)

### Final Answer:
The possible reactions at the anode are:
- **Option C:** 2Cr³⁺ + 7H₂O → Cr₂O₇²⁻ + 14H⁺ + 6e⁻
- **Option D:** Fe²⁺ → Fe³⁺ + e⁻