Haber–Bosch ammonia synthesis: N₂ + 3H₂ ⇌ 2NH₃
ChemistryKinetics & EquilibriumAges 16–17
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Kinetics & Equilibrium
A reaction vessel holds N₂ and H₂ molecules; once running, they collide and gradually convert to NH₃ until equilibrium is reached. Drag pressure, temperature, and the H₂ : N₂ mole ratio, and toggle the iron catalyst, to see the equilibrium yield and the time to reach it change exactly as Le Chatelier's principle predicts. A Plant design tab weighs yield, rate, energy, plant cost and CO₂ to justify the compromise conditions, and a Contact process tab does the same for making sulfuric acid.
Lesson: Elemental nitrogen and ammonia synthesis; applying Le Chatelier's principle to the N₂ + 3H₂ ⇌ 2NH₃ equilibrium
What it shows
The Haber–Bosch process makes ammonia from nitrogen and hydrogen in a reversible, exothermic reaction that reduces four molecules of gas to two. High pressure and low temperature favor ammonia, yet at low temperature equilibrium is reached far too slowly, and every extra atmosphere costs energy and a stronger plant. The iron catalyst speeds up both directions without changing the equilibrium yield, and recycling the unreacted gas lets almost all of it become ammonia. The Contact process faces the same trade-offs for 2SO₂ + O₂ ⇌ 2SO₃ over V₂O₅, then absorbs SO₃ in concentrated sulfuric acid to form oleum.
How to use
On Equilibrium, press Run and change one control at a time to compare the equilibrium yield and the time to reach it. On Plant design, set the Temperature and Pressure, switch the Iron catalyst and Recycle unreacted gas, and press Record design to compare yield, production, energy, CO₂ and cost per tonne. On Contact process, do the same with the V₂O₅ catalyst, Double absorption and Absorb SO₃.
Parameters you can change
- Pressure 10–400 atm
- Temperature 300–600 °C
- Iron powder catalyst
- H₂ : N₂ mole ratio 1 : 1, 2 : 1, 3 : 1 (stoichiometric), 4 : 1
- Screen Equilibrium, Plant design, Contact process
- Plant temperature 300–600 °C
- Plant pressure 50–400 atm
- Iron catalyst in the plant
- Recycle unreacted gas
- Contact process temperature 350–650 °C
- Contact process pressure 1–10 atm
- V₂O₅ catalyst
- Double absorption
- Absorb SO₃ in 98% H₂SO₄, in water
Questions to explore
- Why is ammonia not made at low temperature, even though the equilibrium yield is higher there?
- Which H₂ : N₂ mole ratio matches the coefficients of the equation, and why?
- How does the iron catalyst affect the equilibrium yield and the time needed to reach equilibrium?
- Why does a Haber plant recycle the nitrogen and hydrogen that did not react?
- Why is SO₃ absorbed in concentrated sulfuric acid rather than in water?
