# Haber-Bosch method for ammonia

> Making ammonia from nitrogen and hydrogen


## Objectives

- State that ammonia is made industrially from nitrogen and hydrogen by the Haber-Bosch method.
- Read the book's equation with its conditions: 500 °C, 200 atm and iron as the catalyst.
- Use the equation's numbers: 3 H₂ give 2 NH₃.

## 1. Magnetic properties and catalytic activity




## 2. Ammonia from air

Predict: which gas must react with nitrogen to give $\ce{NH3}$?

- No other gas: nitrogen alone becomes ammonia
- Oxygen
- Hydrogen ✓

$\ce{NH3}$ is made of nitrogen and hydrogen, so nitrogen must react with hydrogen: $\ce{N2 + 3H2 -> 2NH3}$.

[ar-EG] الـ $\ce{NH3}$ متكوّنة من nitrogen و hydrogen، يبقى الـ nitrogen لازم يتفاعل مع الـ hydrogen: $\ce{N2 + 3H2 -> 2NH3}$.
## 3. The book's equation

Preparation of ammonia by the Haber-Bosch method (book p.15) Read it: nitrogen gas and hydrogen gas give ammonia gas. One $\ce{N2}$ reacts with three $\ce{H2}$ to give two $\ce{NH3}$. Over the arrow: 500 °C, a pressure of 200 atm, and iron, Fe, the catalyst. 200 atm (atmospheres) is 200 times normal air pressure.


## 4. Why iron is needed

The bond in $\ce{N2}$ is very strong. Breaking it needs a high activation energy, so the reaction is very slow. Iron, a transition element, lowers the activation energy. So ammonia forms fast enough for a factory. The same reaction without and with iron Fe is a reactant: it reacts with nitrogen and hydrogen to make ammonia.


## 5. Use the equation

In the Haber-Bosch method, 6 molecules of $\ce{H2}$ react completely with enough $\ce{N2}$. How many molecules of $\ce{NH3}$ form? Which statement about the iron in the Haber-Bosch method is correct?


## 6. Summary

Ammonia is made industrially from nitrogen and hydrogen by the Haber-Bosch method. $\begin{gathered}\ce{N2(g) + 3H2(g) ->[500\,^{\circ}C / 200\,atm,\ Fe]}\\ \ce{2NH3(g)}\end{gathered}$ Iron is the catalyst: it lowers the activation energy of this slow reaction. Iron, nickel and $\ce{V2O5}$ as catalysts in industry. Can you explain why iron is written over the arrow and not as a reactant? Iron is the catalyst, not a reactant: it lowers the activation energy and speeds up the reaction, but it is not used up and gives no extra ammonia. That is why it sits over the arrow.



Chapter: Transition Elements (https://yaani.ai/ar/learn/chemistry/chem-s3-en.ch1)
Source: https://yaani.ai/ar/lesson/chem-s3-en.lesson-chem.ammonia-haber