# Extraction by carbon

Metals less reactive than carbon, such as iron, are extracted by heating their oxide with carbon. The carbon takes the oxygen away.

Chemistry (school) · Part 07: Metals and electrolysis · Card 6 of 9 · Last updated 2026-10-19

## Analogy

The carbon is a more powerful magnet for oxygen than the metal.

## Example

**Blast furnace**

iron oxide + carbon
-> iron + carbon dioxide
2Fe2O3 + 3C -> 4Fe + 3CO2

## In practice

Iron is made in a blast furnace by heating iron oxide with carbon.

## Practice

### Flashcards

- **Which method extracts metals more reactive than carbon?** Electrolysis.

### Interview questions

**Explain why aluminium is extracted by electrolysis but iron can be extracted with carbon.**

- Aluminium is more reactive than carbon
- Carbon cannot displace aluminium from its oxide
- Iron is less reactive than carbon
- Electrolysis needs a lot of electricity so it costs more

## Questions people ask

### What does the blast furnace do?

It is a tall furnace where iron ore, coke (carbon) and limestone are fed in at the top and hot air is blown in at the bottom. Carbon reacts with oxygen to give carbon monoxide, which removes oxygen from iron oxide to give molten iron.

### Why is limestone added to the blast furnace?

Iron ore contains impurities such as sand, silicon dioxide. Limestone breaks down on heating to give calcium oxide, which reacts with the sand to make slag, a molten waste that floats on the iron. The slag can then be removed and often used in road building.

## Related concepts

- [Electrolysis](https://studyvisually.com/learn/science/chemistry-school/chemistry-school-part-7/chemistry-school-part-7-concept-7)
- [Reactivity series](https://studyvisually.com/learn/science/chemistry-school/chemistry-school-part-7/chemistry-school-part-7-concept-1)
- [Ore](https://studyvisually.com/learn/science/chemistry-school/chemistry-school-part-7/chemistry-school-part-7-concept-5)

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