During extraction of iron from haematite, the flux used is _______.

Answer

**Step-by-Step Solution:**

1. **Identify the Ore**: The question refers to the extraction of iron from hematite. Hematite is an iron ore with the chemical formula Fe2O3.

2. **Understand the Role of Flux**: In metallurgy, a flux is a substance added to the ore during the extraction process to help remove impurities. The impurities in iron ore are often silicates, which need to be removed to obtain pure iron.

3. **Identify the Flux Used**: The flux used during the extraction of iron from hematite is limestone, which is primarily composed of calcium carbonate (CaCO3).

4. **Process of Calcination**: When limestone is heated (calcinated), it decomposes into calcium oxide (CaO) and carbon dioxide (CO2). The reaction can be represented as:
\[ \text{CaCO}_3 \, (\text{s}) \rightarrow \text{CaO} \, (\text{s}) + \text{CO}_2 \, (\text{g}) \]

5. **Formation of Slag**: The calcium oxide (CaO) produced from the calcination of limestone acts as a basic flux. It reacts with the acidic gangue material, which is primarily silica (SiO2), to form calcium silicate (CaSiO3), a slag that can be removed from the furnace. The reaction can be represented as:
\[ \text{CaO} \, (\text{s}) + \text{SiO}_2 \, (\text{s}) \rightarrow \text{CaSiO}_3 \, (\text{l}) \]

6. **Conclusion**: Therefore, the flux used during the extraction of iron from hematite is limestone (calcium carbonate).

**Final Answer**: The flux used is limestone.

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