An ore is a rock that contains enough of a metal or a metal compound to make extracting the metal worthwhile:
Most metals are extracted from ores found in the Earth's crust. It is more expensive and wasteful to extract a metal from a low-grade ore, but most high-grade ores have already been used.
The extraction method used depends upon the metal's position in the reactivity series. In principle, any metal could be extracted from its compounds using electrolysis. However, large amounts of electrical energy are needed to do this, so electrolysis is expensive.
If a metal is less reactive than carbon, it can be extracted from its compounds by heating with carbon.
Metal oxide + carbon → metal + carbon dioxide
For example, molten copper can be produced from copper oxide by heating with carbon:
Copper oxide + carbon → copper + carbon dioxide
2CuO(s) + C(s) → 2Cu(l) + CO2(g)
Note: the impure copper is purified by electrolysis.
The table summarises the extraction methods used for different metals.
As iron is below carbon in the reactivity series it can be displaced from its compounds by heating with carbon. Iron is extracted from iron ore in a large container called a blast furnace. Iron(III) oxide is reduced to molten iron when it reacts with carbon. The overall reaction is:
Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g)
The iron oxide is reduced and the carbon is oxidised.
These reactions happen because carbon is more reactive than iron, so it can displace iron from iron compounds. Extracting a metal by heating with carbon is cheaper than using electrolysis.
Write a balanced equation for the reaction between tin(IV) oxide and carbon, forming molten tin and carbon dioxide.
SnO2(s) + C(s) → Sn(l) + CO2(g)