In the metallurgy of aluminium,

Options

A. `Al^(3+)` is oxidized to Al (s).
B. graphide anode is oxidation to carbon monoxide and carbon dioxide.
C. oxidation state of oxygen changes in the reaction at anode.
D. oxidation state of oxygen in the overall reaction changes in the process.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Process**: The metallurgy of aluminum primarily involves the Hall-Heroult process, which is an electrolytic method used to extract aluminum from its ore, bauxite (Al2O3).

2. **Identifying the Reactions**: In the Hall-Heroult process, aluminum oxide (Al2O3) is dissolved in molten cryolite (Na3AlF6) and subjected to electrolysis. The overall reaction can be represented as:
\[ 2Al_2O_3 + 3C \rightarrow 4Al + 3CO_2 \]

3. **Analyzing the Cathode Reaction**: At the cathode, aluminum ions (Al³⁺) gain electrons (reduction) to form solid aluminum (Al):
\[ Al^{3+} + 3e^- \rightarrow Al \]

4. **Analyzing the Anode Reaction**: At the anode, graphite (C) is oxidized. There are two possible reactions:
- Graphite reacts with oxide ions (O²⁻) to produce carbon monoxide (CO):
\[ C + O^{2-} \rightarrow CO + 2e^- \]
- Graphite can also react with two oxide ions to produce carbon dioxide (CO₂):
\[ C + 2O^{2-} \rightarrow CO_2 + 4e^- \]

5. **Determining the Correct Statement**:
- **Statement 1**: "Al³⁺ is oxidized to Al solid" - This is incorrect because Al³⁺ is reduced to Al.
- **Statement 2**: "Graphite anode is oxidized to carbon monoxide and carbon dioxide" - This is correct as graphite is oxidized during the process.
- **Statement 3**: "Oxidation state of oxygen changes in the reaction at anode" - This is incorrect; the oxidation state of oxygen remains -2.
- **Statement 4**: "Oxidation state of oxygen in the overall reaction changes in the process" - This is also incorrect; oxygen retains its oxidation state of -2.

6. **Conclusion**: The only true statement is that the graphite anode is oxidized to carbon monoxide and carbon dioxide. Therefore, the correct answer is **option 2**.

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