Iron is extracted from iron ore in a huge container called a blast furnace. Iron ores such as haematite 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.
Iron(III) oxide + carbon → iron + carbon dioxide
2Fe2O3(s) + 3C(s) → 4Fe(l) + 3CO2(g)
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(s) → 2Fe(l) + 3CO2(g)
|Iron ore (haematite)||Iron(III) oxide||A compound that contains iron|
|Coke||Carbon||Burns in air to produce heat, and reacts to form carbon monoxide (needed to reduce the iron oxide)|
|Limestone||Calcium carbonate||Helps to remove acidic impurities from the iron by reacting with them to form molten slag|
|Air||Oxygen||Allows the coke to burn, and so produces heat|
calcium carbonate → calcium oxide + carbon dioxide
CaCO3(s) → CaO(s) + CO2(g)
The calcium oxide then reacts with silica (sand) impurities in the haematite, to produce slag - which is calcium silicate.
calcium oxide + silica → calcium silicate
CaO(s) + SiO2(s) → CaSiO3(l)