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Difficulty: MediumIron: Blast Furnace Extraction, Rusting Prevention, and Chemical Compounds

Match each chemical substance or process associated with iron extraction and rust prevention on the left with its corresponding chemical role or function on the right.

  • Limestone (CaCO3\text{CaCO}_3)Decomposes thermally to provide calcium oxide, which functions as a basic flux
  • Carbon monoxide (CO\text{CO})Serves as the main reducing agent converting iron oxides to molten iron in the blast furnace
  • GalvanizationProtects iron from rusting by coating it with a sacrificial layer of zinc
  • Calcium silicate (CaSiO3\text{CaSiO}_3)Forms molten slag that floats on top of molten iron, protecting it from re-oxidation

Answer

Limestone (CaCO₃) matches with thermal decomposition to provide calcium oxide as a basic flux. Carbon monoxide (CO) matches with serving as the main reducing agent. Galvanization matches with sacrificial coating of iron using zinc. Calcium silicate (CaSiO₃) matches with forming molten slag that floats on molten iron.
Limestone decomposes into calcium oxide, which acts as a basic flux to neutralize silica impurities. Carbon monoxide is the main gaseous reducing agent reducing hematite to metallic iron. Galvanization applies a protective, sacrificial layer of zinc onto iron surfaces. Calcium silicate forms the molten slag layer that sits above molten iron to protect it from re-oxidation.

Step-by-Step Solution

1
Identify the role of limestone in the blast furnace.
Limestone undergoes endothermic decomposition to form calcium oxide (CaO\text{CaO}), acting as a basic flux.
Flux is required to react with acidic impurities like silicon(IV) oxide.
2
Identify the primary reducing agent in iron extraction.
Carbon monoxide (CO\text{CO}) reduces hematite (Fe2O3\text{Fe}_2\text{O}_3) to iron in the upper and middle zones of the furnace.
At elevated blast furnace temperatures, gaseous carbon monoxide readily abstracts oxygen from iron ores.
3
Determine the role of zinc coating on iron (galvanization).
Galvanization provides sacrificial protection against corrosion.
Zinc oxidizes preferentially to iron because of its higher position in the electrochemical series.
4
Determine the identity and function of slag.
Calcium silicate (CaSiO3\text{CaSiO}_3) constitutes molten slag.
Slag is less dense than liquid iron, floating on top to prevent oxidation by incoming air blasts.

Key Concept

Industrial extraction of iron in the blast furnace and sacrificial protection mechanisms against iron rusting.
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Topics

Iron: Blast Furnace Extraction, Rusting Prevention, and Chemical Compounds

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