Which of the following methods is used for obtaining aluminium metal ?

Options

A. Electrolysing fused `Al_2O_3` and cryolite
B. By heating `Al_2O_3` with carbon
C. By heating `Al_2O_3` in muffle furnace
D. By a process called pyrometallurgy

Answer

To determine the method used for obtaining aluminum metal, we will analyze the options provided and focus on the most commonly accepted method in metallurgy for aluminum extraction.

### Step-by-Step Solution:

1. **Understanding Aluminum Extraction**:
Aluminum is primarily extracted from its ore, bauxite, which contains aluminum oxide (Al2O3). The extraction process involves reducing aluminum oxide to aluminum metal.

2. **Electrolysis of Aluminum Oxide**:
The most widely used method for extracting aluminum is through the electrolysis of aluminum oxide. This process requires the aluminum oxide to be in a molten state, which is achieved by mixing it with cryolite (Na3AlF6) and sometimes calcium fluoride (CaF2). Cryolite serves two main purposes:
- It lowers the melting point of aluminum oxide, making the process more energy-efficient.
- It increases the conductivity of the molten mixture.

3. **Setting Up the Electrolysis**:
In the electrolysis setup, a steel cathode and a graphite anode are used. The aluminum ions (Al^3+) are reduced at the cathode, while the oxide ions (O^2-) are oxidized at the anode.

4. **Overall Reaction**:
The overall reaction during the electrolysis can be summarized as follows:
- At the cathode: Al^3+ + 3e^- → Al (s)
- At the anode: 2O^2- → O2 (g) + 4e^-
- The graphite anode also reacts to produce carbon dioxide (CO2).

5. **Conclusion**:
Therefore, the correct method for obtaining aluminum metal is through the electrolysis of fused aluminum oxide (Al2O3) mixed with cryolite.

### Final Answer:
The method used for obtaining aluminum metal is **Electrolyzing fused Al2O3 and Cryolite**.

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