Obtaining metals from metal oxides

Carbon is a non-metal but it is more reactive than some metals. This means that some metals can be extracted from their metal oxides using carbon.

Less reactive metals than carbon can be extracted from their oxides by heating with carbon. In general:

metal oxide + carbon → metal + carbon dioxide

This works for zinc, iron, tin, lead and copper. Copper is the least reactive of these five metals.

A list of metals from the least reactive to the most reactive and those that can and cannot be extracted using carbon. Those less reactive than carbon can be extracted and those more reactive cannot.Carbon fits between aluminium and zinc in the reactivity series

Extracting copper from copper oxide

Copper water pipes
Copper is so unreactive, it does not react with cold or hot water, so it is used for water pipes

To extract copper, you mix copper oxide powder with carbon powder. You then heat the mixture strongly for a few minutes in a crucible. It is important to keep a lid on the crucible, otherwise the carbon will react with oxygen in the air, rather than with the copper oxide. The carbon dioxide formed in the reaction escapes into the air.

After letting the crucible cool down, you tip the mixture into cold water. Pieces of brown copper sink to the bottom, leaving unreacted powder suspended in the water.

These equations represent the reaction:

copper oxide + carbon → copper + carbon dioxide

2CuO + C → 2Cu + CO2

Scientist Mark Miodownik shows how copper ore can be heated on an open fire to extract the metal

Extracting iron from iron oxide

Iron is less reactive than carbon, so it can be extracted from iron oxide using carbon. This is done on an industrial scale in a huge container called a blast furnace.

Molten steel in blast furnace
A blast furnace is used to produce industrial metals by extracting iron

Lumps of iron oxide are mixed with carbon and dropped into the top of the blast furnace. Hot air is blasted in at the bottom. The oxygen in the air reacts with the carbon, forming carbon monoxide:

carbon + oxygen → carbon monoxide

2C +O2 → 2CO

It is hot enough in the blast furnace for the carbon monoxide to react with the iron oxide:

iron oxide + carbon monoxide → iron + carbon dioxide

Fe2O3 + 3CO → 2Fe + 3CO2

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