Metals less reactive than carbon can be extracted from their oxides by…

The idea

This statement describes a key industrial extraction method. Metals less reactive than carbon can be extracted by heating their oxides with carbon, which removes the oxygen. This is reduction with carbon. For example, copper(II) oxide is reduced directly by carbon: $2CuO + C \rightarrow 2Cu + CO_2$. In the industrial extraction of iron in a blast furnace, carbon is added, but it first reacts to form carbon monoxide, which acts as the main reducing agent: $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$. Metals more reactive than carbon, such as aluminium, cannot be extracted this way because carbon is not reactive enough to displace them; they require electrolysis. You should be able to identify which metals can be extracted with carbon using the reactivity series and write balanced equations for these reduction reactions.

What earns the marks

• States that carbon can extract metals that are less reactive than carbon from their oxides.
• Describes reduction as the removal of oxygen from the metal oxide.
• Writes the general word equation for direct reduction: metal oxide + carbon → metal + carbon dioxide.
• Explains that in the blast furnace, carbon monoxide acts as the primary reducing agent for iron(III) oxide.
• Explains that metals more reactive than carbon cannot be extracted with carbon and require electrolysis instead.
• Uses the reactivity series to decide whether carbon reduction is suitable for a given metal.

Common mistakes and how to put them right

• Writing that carbon can extract any metal from its oxide.

  Put it right: Carbon only works for metals less reactive than carbon.

• Confusing reduction with oxidation.

  Put it right: The metal oxide is reduced (loses oxygen) while carbon is oxidised (gains oxygen).

• Assuming carbon directly reduces iron in the blast furnace.

  Put it right: Carbon monoxide is the actual reducing agent for iron(III) oxide.

Exam tips

• Check the metal's position against carbon in the reactivity series before choosing carbon reduction as the method.
• Be prepared to write balanced symbol equations, distinguishing between direct carbon reduction (e.g. $2CuO + C \rightarrow 2Cu + CO_2$) and carbon monoxide reduction ($Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$).
• Use the phrase 'less reactive than carbon' precisely rather than saying 'low reactivity' without comparison.