8.3.1The Periodic Table
Production of Ammonia — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions
5 min read 4 parts Lesson 11 of 23 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 4Raw Materials and Demand
The Haber process turns nitrogen and hydrogen into ammonia, which is a key raw material for fertilisers.
Nitrogen
- Nitrogen Nitrogen is obtained from the air, which is about four-fifths nitrogen by volume.
Hydrogen
- Hydrogen Hydrogen is obtained from natural gas (methane) or from other sources.
Fertilisers
- Fertilisers Ammonia is a raw material for making fertilisers, which help crops produce higher yields of food.
Demand
- Demand There is a high global demand for fertilisers, which keeps the Haber process in large-scale use.
Section 2 of 4Stages of the Haber Process
The process runs as a continuous cycle with recycling of unreacted gases.
1
Hydrogen and nitrogen gases are pumped through pipes into the compressor.
2
The gases are compressed to about 200 atm and passed over an iron catalyst at about 450 °C.
3
Some of the gases react in the reversible reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), and the rest pass through unchanged.
4
The mixture is cooled, so the ammonia liquefies and is removed to pressurised storage vessels.
5
The unreacted hydrogen and nitrogen are recycled back into the system.
Section 3 of 4Separating and Recycling
Cooling separates the ammonia from the gases that have not reacted.
Separating and Recycling
Boiling point
- Boiling point Ammonia has a higher boiling point than hydrogen and nitrogen, so it condenses first when the mixture is cooled.
Recycling
- Recycling The unreacted gases stay as gases and are returned to the reaction vessel.
Efficiency
- Efficiency Because only some of the gases react on each pass, recycling makes the overall use of reactants efficient.
Storage
- Storage Liquid ammonia is stored under pressure in vessels, ready for use.
Section 4 of 4Exam Checklist & Tips
8.3.1 – Key Points for the Exam
- Haber process The industrial manufacture of ammonia from nitrogen and hydrogen.
- Fertiliser A substance that supplies nutrients to plants, such as nitrogen compounds.
- Liquefy To change from a gas into a liquid by cooling or compression.
- Recycling Returning unreacted reactants to the reaction vessel.
Common Mistakes
- Saying the Haber reaction goes to completion; it is reversible and only partly reaches equilibrium.
- Stating that nitrogen comes from natural gas;
- nitrogen is obtained from the air, and hydrogen comes from natural gas.
- Saying the iron catalyst is used up; it is recovered and reused.
- Stating the conditions without explaining why the gases are compressed to a high pressure.
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