# Iron with non-metals: chlorine and sulphur

> Iron(III) with chlorine, iron(II) with sulphur


## Objectives

- Write the equations of iron with chlorine and with sulphur.
- State the oxidation state of iron in $\ce{FeCl3}$ and in FeS.

## 1. Properties of iron




## 2. Same metal, two partners

Predict: what does iron form with chlorine?

- Nothing: iron reacts only with oxygen
- $\ce{FeCl2}$, iron(II) chloride
- $\ce{FeCl3}$, iron(III) chloride ✓

Heated iron reacts with chlorine to give iron(III) chloride: $\ce{2Fe + 3Cl2 -> 2FeCl3}$. Chlorine takes iron to the +3 oxidation state.

[ar-EG] الـ iron لما يتسخن مع الـ chlorine بيدّي iron(III) chloride: $\ce{2Fe + 3Cl2 -> 2FeCl3}$. الـ chlorine بيوصّل الـ iron للـ oxidation state +3.
## 3. With chlorine: iron(III) chloride

Iron reacts with chlorine producing iron (III) chloride. Each Cl is −1. Three Cl give −3, so iron is +3. Fe + $\ce{Cl2}$ gives $\ce{FeCl2}$.


## 4. With sulphur: iron(II) sulphide

Iron reacts with sulphur producing iron (II) sulphide. Chlorine Strong oxidizing agent → $\ce{FeCl3}$, iron +3 Sulphur Weaker oxidizing agent → FeS, iron +2 In a sulphide, sulphur is −2. So iron is +2 in FeS. Fe + S gives $\ce{FeSO4}$ or $\ce{Fe2S3}$.


## 5. Worked: balancing iron + chlorine

Formulas first: Fe + $\ce{Cl2}$ → $\ce{FeCl3}$. Chlorine gas comes as $\ce{Cl2}$ molecules. Cl: 2 on the left, 3 on the right. The lowest common multiple is 6. 6 Cl = 3 $\ce{Cl2}$ on the left and 2 $\ce{FeCl3}$ on the right. Now there are 2 Fe on the right, so write 2Fe on the left. Check: 2 Fe and 6 Cl on each side.


## 6. Your turn: a new metal

Aluminum also reacts with chlorine on heating, giving $\ce{AlCl3}$. Balance the equation.


## 7. Iron(II) or iron(III)?

A student writes $\ce{Fe + S -> FeSO4}$. What is wrong?

- There is no oxygen on the left, so a sulphate cannot form. ✓
- Nothing: heating iron with sulphur gives a sulphate.
- Iron does not react with sulphur.
- The product should be $\ce{Fe2S3}$, iron(III) sulphide.

The left side holds Fe and S with no oxygen, so a sulphate cannot form. Heated iron and sulphur give iron(II) sulphide: $\ce{Fe + S -> FeS}$.

[ar-EG] الناحية الشمال فيها Fe و S من غير أي oxygen، فمينفعش يتكوّن sulphate. الـ iron والـ sulphur لما يتسخنوا بيدّوا iron(II) sulphide: $\ce{Fe + S -> FeS}$.
## 8. Summary

Iron + chlorine → iron (III) chloride: $\ce{2Fe + 3Cl2 -> 2FeCl3}$. Iron is +3. Iron + sulphur → iron (II) sulphide: $\ce{Fe + S -> FeS}$. Iron is +2. Sulphur is a weaker oxidizing agent than chlorine, so iron stops at +2. No oxygen reacts, so no sulphate forms. MCQ (Q1.1): the reaction of iron and sulphur gives FeS. Can you explain why iron is +3 in $\ce{FeCl3}$ but +2 in FeS? Each Cl is −1, so three Cl give −3 and iron is +3 in $\ce{FeCl3}$. In a sulphide, sulphur is −2, so iron is +2 in FeS. Chlorine is a strong oxidizing agent; sulphur is a weaker one.



Chapter: Transition Elements (https://yaani.ai/en/learn/chemistry/chem-s3-en.ch1)
Source: https://yaani.ai/en/lesson/chem-s3-en.lesson-fe.reactions-nonmetals