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Metals - Extraction of Iron (Blast Furnace)

Grade 11IGCSEChemistry

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The Blast Furnace is used to extract iron from its ore, primarily Hematite (Fe2O3Fe_2O_3).

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Raw materials required: Hematite (Fe2O3Fe_2O_3), Coke (CC), Limestone (CaCO3CaCO_3), and Hot Air (O2O_2).

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Coke reacts with oxygen to produce heat and carbon dioxide (CO2CO_2), which then reacts with more coke to form the reducing agent, carbon monoxide (COCO).

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The reduction of iron(III) oxide occurs as COCO removes oxygen from Fe2O3Fe_2O_3 to form molten iron and CO2CO_2.

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Limestone (CaCO3CaCO_3) undergoes thermal decomposition to form calcium oxide (CaOCaO), which reacts with silica impurities (SiO2SiO_2) to form molten slag (CaSiO3CaSiO_3).

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Molten iron is denser than slag and sinks to the bottom; slag floats on top, preventing the re-oxidation of the molten iron.

📐Formulae

C(s)+O2(g)→CO2(g)C(s) + O_2(g) \rightarrow CO_2(g)

CO2(g)+C(s)→2CO(g)CO_2(g) + C(s) \rightarrow 2CO(g)

Fe2O3(s)+3CO(g)→2Fe(l)+3CO2(g)Fe_2O_3(s) + 3CO(g) \rightarrow 2Fe(l) + 3CO_2(g)

CaCO3(s)→CaO(s)+CO2(g)CaCO_3(s) \rightarrow CaO(s) + CO_2(g)

CaO(s)+SiO2(s)→CaSiO3(l)CaO(s) + SiO_2(s) \rightarrow CaSiO_3(l)

💡Examples

Problem 1:

Explain the chemical role of Limestone (CaCO3CaCO_3) in the extraction of iron and provide the relevant balanced equations.

Solution:

Limestone acts as a flux to remove impurities. It decomposes: CaCO3(s)→CaO(s)+CO2(g)CaCO_3(s) \rightarrow CaO(s) + CO_2(g). The resulting CaOCaO reacts with SiO2SiO_2: CaO(s)+SiO2(s)→CaSiO3(l)CaO(s) + SiO_2(s) \rightarrow CaSiO_3(l).

Explanation:

Iron ore contains sandy impurities like silicon dioxide (SiO2SiO_2), which are acidic. Limestone thermally decomposes into calcium oxide (CaOCaO), a basic oxide. This basic oxide reacts with the acidic SiO2SiO_2 in a neutralization-type reaction to form molten calcium silicate, also known as slag (CaSiO3CaSiO_3).

Problem 2:

Determine the mass of iron that can be produced from 480480 kg of Hematite (Fe2O3Fe_2O_3). (Relative atomic masses: Fe=56,O=16Fe = 56, O = 16)

Solution:

Mass of Fe=336Fe = 336 kg

Explanation:

First, calculate the molar mass (MrM_r) of Fe2O3Fe_2O_3: (2×56)+(3×16)=112+48=160 g/mol(2 \times 56) + (3 \times 16) = 112 + 48 = 160 \text{ g/mol}. The balanced equation shows that 11 mole of Fe2O3Fe_2O_3 produces 22 moles of FeFe. Therefore, 160160 kg of Fe2O3Fe_2O_3 produces 112112 kg of FeFe. For 480480 kg of ore: 480160×112=3×112=336 kg\frac{480}{160} \times 112 = 3 \times 112 = 336 \text{ kg}.

Extraction of Iron (Blast Furnace) Revision - Grade 11 Chemistry IGCSE