9.3.2Metals
Extraction of Iron from Hematite — Combined Science 0653 - Chemistry Revision Notes & Topical Questions
5 min read 6 parts Lesson 7 of 11 Unit quiz
Part 1 of 5Inside the blast furnace
Raw materials
- Raw materials Hematite (iron ore, mainly iron(III) oxide), coke (impure carbon) and limestone are fed in at the top.
- Hot air is blown in near the bottom.
Output
- Output Molten iron collects at the base and is tapped off.
- A large modern furnace makes around ten thousand tonnes per day.
Why reduction
- Why reduction Iron is below carbon in the reactivity series, so carbon can remove oxygen from its oxide.
Part 2 of 5Reactions in order
1Coke burns
- Coke burns Carbon + oxygen → carbon dioxide. This is exothermic and heats the furnace.
2Carbon monoxide forms
- Carbon monoxide forms Carbon + carbon dioxide → carbon monoxide, the main reducing agent.
3Iron oxide reduced
- Iron oxide reduced Iron(III) oxide + carbon monoxide → iron + carbon dioxide.
- Oxygen is removed, so the iron ore is reduced.
4Iron runs down
- Iron runs down Liquid iron is dense, trickles to the bottom and is tapped off.
Part 3 of 5Symbol equations (HT only)
| Stage | Balanced equation |
|---|---|
| Burning coke | C(s) + O2(g) → CO2(g) |
| Making carbon monoxide | CO2(g) + C(s) → 2CO(g) |
| Reducing the ore | Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g) |
| Decomposing limestone | CaCO3(s) → CaO(s) + CO2(g) |
| Forming slag | CaO(s) + SiO2(s) → CaSiO3(l) |
Part 4 of 5Removing impurities with limestone
1
The ore contains impurities, mainly silicon dioxide (sand), which would clog the furnace.
2
In the heat, limestone (calcium carbonate) thermally decomposes into calcium oxide and carbon dioxide.
3
Calcium oxide is a basic oxide and reacts with the acidic silicon dioxide to form calcium silicate.
4
Calcium silicate melts and is called slag. It is less dense than iron, so it floats on top and is tapped off separately.
5
Slag can be used for road building.
Part 5 of 5Key ideas to link
Blast furnace
Heat
- Heat Burning coke provides the very high temperature.
Reduction
- Reduction Carbon monoxide takes the oxygen from iron(III) oxide.
Purification
- Purification Limestone turns sand into slag, which is separated from the iron.
Core and Extended
- Core and Extended Word equations are needed for all candidates;
- symbol equations are required for the extended tier (HT only).
Key terms
| Term | Meaning |
|---|---|
| Hematite | The main ore of iron, mainly iron(III) oxide, Fe2O3. |
| Coke | An impure form of carbon used as a fuel and to make the reducing agent. |
| Reduction | Removal of oxygen from a compound (or gain of electrons). |
| Slag | Molten calcium silicate formed from limestone and sand; it floats on the iron. |
| Thermal decomposition | Breaking down of a compound by heat. |
Avoid these mistakes
1
Saying carbon itself reduces the ore directly. The main reducing agent is carbon monoxide.
2
Stating that limestone reduces the ore. It removes impurities by forming slag.
3
Forgetting that the reaction of carbon with oxygen is exothermic and supplies heat.
4
Writing the iron product as solid. In the furnace, iron is molten (l) and runs to the bottom.
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