Iron is extracted from iron ore in a huge container called a blast furnace. Iron ores such as hematite contain iron(III) oxide, Fe2O3. The oxygen must be removed from the iron(III) oxide in order to leave the iron behind. Reactions in which oxygen is removed are called reduction reactions.
Carbon is more reactive than iron, so it can displace iron from iron(III) oxide. Here are the equations for the reaction.
Step 1 – Hot air (oxygen) reacts with the coke (carbon) to produce carbon dioxide and heat energy to heat up the furnace.
C(s) + O2(g) → CO2(g)
Step 2 – More coke is added to the furnace and reduces the carbon dioxide into carbon monoxide, a good reducing agent.
CO2(g) + C(s) → 2CO(g)
Step 3 – iron(III) oxide is reduced.
iron(III) oxide + carbon → iron + carbon dioxide
2Fe2O3(s) + 3C(s) → 4Fe(l) + 3CO2(g)
In this reaction, the iron(III) oxide is reduced to iron, and the carbon is oxidized to carbon dioxide.
In the blast furnace, it is so hot that carbon monoxide can be used, in place of carbon, to reduce the iron(III) oxide:
iron(III) oxide + carbon monoxide → iron + carbon dioxide
Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g)
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