In extraction of aluminium from bauxite ore, reduction is carried out by :

Options

A. carbon
B. magnesium
C. electrolysis
D. hydrogen

Answer

To solve the question regarding the extraction of aluminum from bauxite ore, we will follow these steps:

### Step 1: Identify the Ore
The ore mentioned is bauxite, which is primarily composed of aluminum oxide (Al2O3) and water (H2O). The formula for bauxite is Al2O3·2H2O.

**Hint:** Remember that the composition of the ore is crucial for understanding the extraction process.

### Step 2: Understand the Reduction Process
In metallurgy, reduction refers to the process of extracting a metal from its ore by removing oxygen or other elements. For aluminum extraction, this process is typically done through electrolysis.

**Hint:** Reduction is the opposite of oxidation, and in the context of metal extraction, it often involves the removal of oxygen.

### Step 3: Identify the Method of Reduction
The reduction of aluminum from bauxite is carried out using electrolysis. During this process, aluminum ions are reduced at the cathode, while oxidation occurs at the anode.

**Hint:** Electrolysis involves passing an electric current through a molten or dissolved ionic compound to cause a chemical change.

### Step 4: Describe the Electrolytic Cell
In the electrolytic cell used for aluminum extraction:
- The anode is made of graphite, which acts as an electrode and provides electrons for the reduction process.
- The cathode is where aluminum ions are reduced to form aluminum metal.
- The electrolyte used is a mixture of aluminum oxide (Al2O3) and cryolite (Na3AlF6), along with calcium fluoride (CaF2).

**Hint:** The choice of electrolyte is important as it lowers the melting point and increases the conductivity of the solution.

### Step 5: Write the Reactions
At the anode, oxidation occurs:
\[ \text{C} + 2 \text{O}^{2-} \rightarrow \text{CO}_2 + 4 \text{e}^- \]

At the cathode, reduction occurs:
\[ 2 \text{Al}^{3+} + 6 \text{e}^- \rightarrow 2 \text{Al} \]

**Hint:** Balancing the reactions is essential to understand the flow of electrons and the overall process.

### Conclusion
Based on the above steps, the correct answer to the question is that the reduction of aluminum from bauxite ore is carried out by **electrolysis**.

**Final Answer:** Option 3: Electrolysis