GCSE · Chemistry · AQA · Spec 8462

The Haber process (chem only)

A factory cannot maximise speed, yield and cost at the same time — follow the Haber loop, then see where the compromises appear.

Follow the Haber loop

1N₂ + H₂ in2345

Stage 1 of 5: N₂ + H₂ in. paused

N₂ + H₂ in · 1/5Scrub from feed gases to recycle.

Purified nitrogen and hydrogen enter.

Step through the factory sequence, then notice what is removed and what is recycled.

Why cool and recycle?

Use the separation step, not equilibrium theory.

After the reactor, why is the mixture cooled and the remaining nitrogen and hydrogen recycled?

The temperature compromise

?

Reason it through

Why not simply use a very low temperature if it gives a better equilibrium yield of ammonia?

Link 1 of 3

First link · your turn

The forward formation of ammonia is exothermic. What does lowering temperature do to the equilibrium yield?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
UK note

AQA GCSE Chemistry: the temperature/equilibrium trade-off reasoning in this block is Higher Tier.

Relationship matrix

Tap any cell to reveal it. Tap a column header to read one property down every item.

Effect on rateEffect on equilibriumCommercial trade-off
Higher temperaturetemperature choice
Higher pressurepressure choice
Iron catalystreaction pathway

Each cell hides a short answer and the reason behind it. Predict before you tap.

UK note

AQA GCSE Chemistry: the commercial-condition reasoning in this block is Higher Tier.

CHEMISTRY

Follow nitrogen and hydrogen through the recycle loop, then see why faster production can fight a better equilibrium yield.

What you need to know

  • The Haber process manufactures ammonia from nitrogen and hydrogen.
  • Nitrogen comes from air and hydrogen commonly comes from natural gas.
  • The gases react over an iron catalyst at high temperature and high pressure, then ammonia is removed by cooling and the unused gases are recycled.
  • Temperature, pressure and catalyst choices affect the reaction rate, the position of equilibrium and the commercial cost of the process.

The big picture

The Haber process makes ammonia from nitrogen and hydrogen, then separates the ammonia and recycles unreacted gases. Commercial conditions balance reaction rate, equilibrium yield and cost.

Key points

1The Haber process manufactures ammonia from nitrogen and hydrogen.
2Nitrogen is obtained from air; hydrogen is commonly obtained from natural gas.
3Purified gases react over an iron catalyst at high temperature and high pressure.
4The reaction is reversible, so not all nitrogen and hydrogen become ammonia in one pass.
5Cooling liquefies ammonia so it can be removed; unreacted nitrogen and hydrogen are recycled.
6commercial conditions balance reaction rate, equilibrium yield and cost.

Worked example

Problem

A factory cools the reaction mixture after the Haber reactor. Explain why this helps the process use its raw materials efficiently.

🧠

Memory hook

React → cool → remove → recycle. The product leaves; the unused gases go round again.

★ Exam tip

AQA Higher Tier: for a commercial-conditions question, explain both sides of the compromise — what the condition does to rate, what it does to equilibrium yield, and why cost matters.

⚠ Watch out

Do not say the iron catalyst increases the equilibrium yield. It speeds the approach to equilibrium but does not change the equilibrium position.

✓

Check yourself

Without looking: what happens to ammonia after cooling, and what happens to nitrogen and hydrogen that did not react?

Flashcards

(20)
What does the Haber process manufacture?
Ammonia.
What can ammonia from the Haber process be used to make?
Nitrogen-based fertilisers.
What are the raw materials for the Haber process?
Nitrogen and hydrogen.
Give a source of nitrogen for the Haber process.
Air.
Give a common source of hydrogen for the Haber process.
Natural gas.
What happens to the gases before they enter the Haber reactor?
They are purified.
Which catalyst is used in the Haber process?
Iron.
What broad temperature and pressure conditions are used?
High temperature and high pressure.
Is the Haber reaction reversible?
Yes.
Why is not all ammonia retained as ammonia in the reactor?
The reaction is reversible, so some ammonia breaks down again into nitrogen and hydrogen.
What happens to ammonia when the mixture is cooled?
It liquefies.
Why is liquefying ammonia useful?
It allows ammonia to be removed from the unreacted gases.
What happens to unreacted nitrogen and hydrogen?
They are recycled through the process.
Why recycle nitrogen and hydrogen?
To reduce waste and give unreacted gases another chance to form ammonia.
What is the temperature trade-off?
Lower temperature favours ammonia at equilibrium but slows the rate; higher temperature speeds the rate but lowers the equilibrium yield.
Why does higher pressure favour ammonia?
The ammonia side has fewer gas particles, so higher pressure favours that side of the equilibrium.
How does higher pressure affect rate?
It increases the rate because gas particles are closer together and collide more often.
What does the iron catalyst do to activation energy?
It provides a pathway with lower activation energy.
Does the catalyst change equilibrium position?
No. It speeds both directions and makes equilibrium reached faster.
What three things are balanced in commercial Haber conditions?
Reaction rate, equilibrium yield and cost/energy use.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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