Limestone's role in removing impurities during iron extraction

Steps:

• Haematite (Fe2O3) is reduced to iron using coke as a reducing agent in the blast furnace.
• Limestone (CaCO3) is added to handle impurities like silica (SiO2) in the ore.
• Heat causes limestone to decompose: CaCO3 → CaO + CO2.
• Calcium oxide (CaO) reacts with acidic silica to form slag: CaO + SiO2 → CaSiO3, which is removed.

Why A is correct:

• Limestone decomposes to calcium oxide, a base that neutralizes acidic impurities like silica per the acid-base reaction CaO + SiO2 → CaSiO3 (slag).

Why the others are wrong:

• B: Coke provides the fuel and heat; limestone acts as a flux, not a fuel.
• C: Coke burns with oxygen from air blasts; limestone does not release oxygen.
• D: Haematite's iron is already oxidized and needs reduction, not further oxidation.

Final answer: A