iGCSE Chemistry (0620) Core:9.6 Extraction of metals: Exam Style Questions Paper 1

Question

Which statement about the extraction of iron from hematite is correct?

A) Air is blown into the blast furnace to oxidise the molten iron.
B) Carbon dioxide is reduced by coke to carbon monoxide.
C) Hematite is oxidised by carbon to molten iron.
D) The slag produced is denser than molten iron.

▶️ Answer/Explanation

Solution

Ans: B

Let’s analyze each option:

Option A: Incorrect – Air is blown in to burn coke (carbon) to produce heat and carbon monoxide, not to oxidize iron.

Option B: Correct – CO₂ reacts with more coke (C) to form CO: CO₂ + C → 2CO

Option C: Incorrect – Hematite (Fe₂O₃) is reduced by CO, not oxidized.

Option D: Incorrect – Slag (calcium silicate) is less dense than molten iron and floats on top.

The key reaction in the blast furnace is the reduction of CO₂ to CO by coke, making option B correct.

Question

Iron is extracted from its ore in the blast furnace.

Which statement about one of the reactions in the blast furnace is correct?

A) Carbon monoxide is reduced to carbon dioxide.
B) Iron(III) oxide is reduced by carbon dioxide.
C) Slag is produced when calcium carbonate reacts with carbon dioxide.
D) The reaction that heats the blast furnace produces carbon dioxide.

▶️ Answer/Explanation

Solution

Ans: D

In the blast furnace:

A) Incorrect – Carbon monoxide is oxidized to carbon dioxide when it reduces iron(III) oxide, not reduced.

B) Incorrect – Iron(III) oxide is reduced by carbon monoxide, not carbon dioxide.

C) Incorrect – Slag is produced when calcium oxide (from the decomposition of calcium carbonate) reacts with silicon dioxide (impurity).

D) Correct – The exothermic reaction of coke (carbon) with oxygen to produce carbon dioxide provides the heat needed for the process.

The key reactions are:
\( \text{C} + \text{O}_2 \rightarrow \text{CO}_2 \) (heat-producing reaction)
\( \text{CO}_2 + \text{C} \rightarrow 2\text{CO} \)
\( \text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2 \) (reduction of iron ore)

Question

Iron from a blast furnace is treated with oxygen and with calcium oxide to make steel.
Which substances in the iron are removed?

▶️Answer/Explanation

Ans: A

During the steelmaking process in a basic oxygen furnace (BOF) or oxygen converter, a controlled stream of pure oxygen is blown onto the molten iron. The oxygen reacts with the carbon in the iron to form carbon monoxide (CO) and carbon dioxide.

During the steelmaking process, the impurities present in the iron, such as silicon oxide , manganese oxide (MnO), and phosphorus oxide, are considered acidic impurities. Calcium oxide reacts with these acidic oxides to form slag, which is a molten mixture of various oxides.

Question

Four equations are shown.
1\( C + O_2 \rightarrow CO_2\)
2 \(CaCO_3 \rightarrow CaO + CO_2\)
3 \(SiO_2 + 2CO \rightarrow Si + 2CO_2\)
4 \(Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2\)
Which equations represent reactions that take place during the extraction of iron from hematite?
A 1, 2 and 3 B 1, 2 and 4 C 2, 3 and 4 D 3 and 4 only

▶️Answer/Explanation

Ans: B

In the blast furnace, carbon monoxide (CO) acts as the reducing agent. It reacts with hematite to produce elemental iron (Fe) and carbon dioxide. This is the main reduction reaction that yields iron in the form of molten metal.

In the blast furnace, coke (carbon) is used as a fuel to provide the heat required for the reduction process. It reacts with oxygen (from air blown into the furnace) to produce carbon dioxide as a byproduct.

In the blast furnace, calcium carbonate decomposes when heated, producing calcium oxide, commonly known as quicklime, and carbon dioxide gas. The calcium oxide then reacts with the acidic impurities in the iron ore, such as silica, to form calcium silicate, which constitutes the slag.

iGCSE Chemistry (0620) Core:9.6 Extraction of metals: Exam Style Questions Paper 1

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