# Iron reacts with sulfur according to the equation: Fe + S → FeS. A student reacts 56 g of iron with an excess of sulfur. Explain what is meant by the term 'limiting reactant' and explain why, in this reaction, iron is the limiting reactant and not sulfur.

> WJEC A-Level Chemistry (Wales) — 3.6 Amines and polymers (A-Level only) · Explain · 5 marks

> Iron reacts with sulfur according to the equation: Fe + S → FeS. A student reacts 56 g of iron with an excess of sulfur.

## Mark scheme (5 marks)

1. The limiting reactant is the reactant that is completely used up during the reaction
2. The limiting reactant limits the amount of product(s) formed
3. Sulfur is present in excess, meaning there is more sulfur than is needed to react with all the iron
4. Iron is completely used up / all 56 g of iron reacts
5. Because iron is used up first/completely, it limits the amount of FeS that can be formed, so iron is the limiting reactant

## Key terms

- [limiting reactant](https://www.gradenine.co.uk/glossary/limiting-reactant)
- [excess](https://www.gradenine.co.uk/glossary/excess)

## Related

- [Revision notes for WJEC A-Level Chemistry (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/iron-reacts-with-sulfur-according-to-f9a51acd) · Published by Druglandscape Ltd.