# Iron with dilute acids

> Iron(II) salts, not iron(III) salts


## Objectives

- Write the equations of iron with dilute sulphuric and hydrochloric acids.
- Give the book's reason why iron(II) salts, not iron(III) salts, form.

## 1. Properties of iron




## 2. Chlorine vs hydrochloric acid

Predict: what does iron give with dilute hydrochloric acid?

- $\ce{FeCl2}$ + hydrogen ✓
- No reaction
- $\ce{FeCl3}$ + hydrogen

Iron with dilute hydrochloric acid gives iron(II) chloride and hydrogen gas: $\ce{Fe + 2HCl -> FeCl2 + H2}$. The hydrogen produced reduces iron(III) to iron(II), so $\ce{FeCl3}$ does not form here.

[ar-EG] الـ iron مع الـ dilute hydrochloric acid بيدّي iron(II) chloride و hydrogen gas: $\ce{Fe + 2HCl -> FeCl2 + H2}$. الـ hydrogen اللي بيطلع بيعمل reduction للـ iron(III) ويرجّعه iron(II)، عشان كده الـ $\ce{FeCl3}$ مش بيتكوّن هنا.
## 3. Iron dissolves in dilute acids

Iron dissolves in dilute mineral acids producing iron (II) salts. Mineral acids Inorganic acids, such as hydrochloric acid (HCl) and sulphuric acid ($\ce{H2SO4}$). Iron does not react with dilute acids.


## 4. Why iron(II), not iron(III)?

The book: iron (II) salts form, not iron (III) salts, which are reduced by the produced hydrogen. Fe + $\ce{Cl2}$ gives $\ce{FeCl3}$, so Fe + HCl gives $\ce{FeCl3}$.


## 5. Worked, then faded

Iron gives an iron(II) salt: $\ce{Fe^{2+}}$. Sulphuric acid gives sulphate, $\ce{SO4^{2-}}$: so $\ce{FeSO4}$. The other product is hydrogen gas, $\ce{H2}$. Write (dil) over the arrow, and the states. Now a new acid, dilute hydrobromic acid: Fe + 2HBr → ___ + $\ce{H2}$


## 6. Give the reason

Give reason: iron reacts with dilute acids to produce iron (II) salts, not iron (III) salts.

- Dilute acids contain no chlorine or sulphate.
- Iron has no +3 oxidation state.
- Iron (III) is unstable, so it never forms.
- The hydrogen produced reduces iron (III) to iron (II). ✓

The book's reason: iron dissolves in dilute mineral acids giving iron(II) salts, because the hydrogen produced reduces iron(III) to iron(II).

[ar-EG] سبب الكتاب: الـ iron بيدوب في الـ dilute mineral acids ويدّي iron(II) salts، عشان الـ hydrogen اللي بيطلع من التفاعل بيعمل reduction للـ iron(III) ويحوّله iron(II).
## 7. Summary

Iron dissolves in dilute mineral acids: iron (II) salt + hydrogen. $\ce{Fe + H2SO4 -> FeSO4 + H2}$ and $\ce{Fe + 2HCl -> FeCl2 + H2}$. Reason: the produced hydrogen reduces iron (III) to iron (II). Contrast: chlorine gas gives $\ce{FeCl3}$. Give reason (Q7.7): iron gives iron (II) salts with dilute acids. Key words: reduced by the produced hydrogen. Can you explain why HCl gives $\ce{FeCl2}$, but chlorine gives $\ce{FeCl3}$? With HCl, hydrogen forms, and the produced hydrogen reduces iron (III) to iron (II): so $\ce{FeCl2}$ forms. Chlorine gas forms no hydrogen, so iron ends as $\ce{FeCl3}$.



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