# Iron reacts with sulfur to form iron(II) sulfide. The balanced symbol equation for this reaction is: Fe + S → FeS. State the type of substance that iron(II) sulfide is and explain why the formula FeS, rather than Fe₂S₂, is used as the chemical formula for iron(II) sulfide.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 1.5 Chemical formulae, equations and calculations · Explain · 4 marks

> Iron reacts with sulfur when heated together. The balanced symbol equation for this reaction is: Fe + S → FeS.

## Mark scheme (4 marks)

1. Iron(II) sulfide is a compound
2. The empirical formula gives the simplest whole number ratio of atoms of each element in the compound
3. Fe₂S₂ can be simplified / divided by 2 to give FeS (ratio 1:1)
4. FeS is the empirical formula (of iron(II) sulfide)

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