# Effect of air and water vapour

> Red-hot iron gives magnetic iron oxide


## Objectives

- Write the equations of red-hot iron with dry air and with water vapour, with their conditions.
- Name the product, magnetic iron oxide, and say which reactant is reduced by iron.

## 1. Properties of iron




## 2. Red-hot iron in oxygen

Predict: which oxide forms on red-hot iron in dry oxygen?

- $\ce{Fe3O4}$, magnetic iron oxide ✓
- $\ce{Fe2O3}$, like hematite
- None: iron only rusts in damp air

Red-hot iron reacts with dry air or oxygen to give magnetic iron oxide, $\ce{Fe3O4}$: $\ce{3Fe + 2O2 -> Fe3O4}$.

[ar-EG] الـ iron وهو أحمر من السخونية بيتفاعل مع الهوا الجاف أو الـ oxygen ويدّي magnetic iron oxide، $\ce{Fe3O4}$: $\ce{3Fe + 2O2 -> Fe3O4}$.
## 3. Effect of air

Red hot iron reacts with dry air or oxygen producing magnetic iron oxide. Magnetic iron oxide $\ce{Fe3O4}$: a black oxide that is attracted by a magnet. In nature it is the ore magnetite. Why 3 and 2? $\ce{Fe3O4}$ holds 3 Fe atoms, so write 3Fe. $\ce{Fe3O4}$ holds 4 O atoms. That is 2 $\ce{O2}$ molecules. Iron gains oxygen, so iron is oxidized.


## 4. Effect of water vapour

Red hot iron (500 °C) reacts with water vapour producing magnetic iron oxide and hydrogen gas. Not balanced yet: you will balance it next. Water vapour gives its oxygen to iron. So water vapour is reduced to hydrogen. Iron and steam give $\ce{Fe(OH)2}$ or $\ce{Fe2O3}$.


## 5. Balance the water vapour equation

Balance the equation of red hot iron with water vapour.


## 6. Air or water vapour?

Experiment A: red hot iron in dry air. Experiment B: red hot iron (500 °C) in water vapour. Which statement is correct?

- B gives $\ce{Fe(OH)2}$ and hydrogen gas.
- A gives $\ce{Fe2O3}$; B gives $\ce{Fe3O4}$.
- Both give hydrogen gas.
- Both give $\ce{Fe3O4}$; only B also gives hydrogen gas. ✓

Both experiments give magnetic iron oxide, $\ce{Fe3O4}$. In B, the water vapour also releases hydrogen gas: $\ce{3Fe + 4H2O -> Fe3O4 + 4H2}$. In A, iron reacts with the oxygen of the air, so no hydrogen forms.

[ar-EG] التجربتين بيدّوا magnetic iron oxide، $\ce{Fe3O4}$. في تجربة B الـ water vapour كمان بيطلّع hydrogen gas: $\ce{3Fe + 4H2O -> Fe3O4 + 4H2}$. أما في A فالـ iron بيتفاعل مع الـ oxygen اللي في الهوا، فمفيش hydrogen بيتكوّن.
## 7. Summary

Red hot iron + dry air or oxygen → $\ce{Fe3O4}$, magnetic iron oxide. Red hot iron (500 °C) + water vapour → $\ce{Fe3O4}$ + hydrogen gas. Iron is oxidized in both. Water vapour is reduced to hydrogen. Write both equations with their conditions: Δ for air, 500 °C for water vapour. Can you explain why water vapour, not iron, is the substance reduced? Water vapour gives its oxygen to iron, so water vapour is reduced to hydrogen. Iron gains that oxygen, so iron is oxidized.



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