Limestone's role in removing impurities during iron extraction

Steps:

• Iron ore (Fe₂O₃) is reduced by carbon monoxide from coke in the blast furnace.
• Coke burns with oxygen from hot air to produce heat and CO for reduction.
• Limestone (CaCO₃) decomposes at high temperature to form CaO and CO₂.
• CaO reacts with acidic impurities like silica (SiO₂) to form slag (CaSiO₃), which is removed.

Why C is correct:

• Limestone decomposes to CaO, a base that neutralizes acidic impurities (e.g., SiO₂) via CaO + SiO₂ → CaSiO₃, preventing contamination of iron.

Why the others are wrong:

• A: Limestone decomposes to CO₂, not oxygen; oxygen for burning coke comes from air.
• B: Limestone releases no oxygen; iron is reduced (gains electrons), not oxidized.
• D: Limestone does not react with coke; heat comes from coke combustion with air.

Final answer: C