Name the principal ore of aluminium. Explain the significance of leaching in the extraction of aluminium.

Explanation

### Step-by-Step Solution:

1. **Identify the Principal Ore of Aluminium**:
- The principal ore of aluminium is **bauxite**. Bauxite is primarily composed of aluminium oxide minerals, along with impurities such as silica, iron oxides, and titanium dioxide.

2. **Explain the Significance of Leaching in the Extraction of Aluminium**:
- **Leaching Process**: Leaching is a hydrometallurgical process that involves the treatment of the ore with a solvent to dissolve the desired metal or mineral. In the case of bauxite, a solution of sodium hydroxide (NaOH) is commonly used.
- **Removal of Impurities**: The significance of leaching lies in its ability to remove impurities from the bauxite ore. During the leaching process, the sodium hydroxide reacts with aluminium oxide (Al2O3) in the bauxite to form soluble sodium aluminate, while impurities such as silica (SiO2) and iron oxides (Fe2O3) remain insoluble and can be separated.
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