19.1 Ammonia – Haber process

Ammonia gas is one of the most important chemicals produced globally for industrial use. Urea and other ammonium salts are extensively used as fertilizers. About 80% of the ammonia produced in the industries world-wide are used to produce these fertilizers. Apart from this, ammonia is also used in the production of plastics and pharmaceuticals. It is also used as a refrigerant.

Ammonia is produced industrially by Haber process discovered by a German Chemist F.J. Haber. In this process, a mixture of nitrogen and hydrogen, in the ratio of 1:3 by volume is heated at 400-500°C under 200 atmospheric pressure and in the presence of catalyst Fe/Al₂O₃ to give ammonia.

The equilibrium mixture obtained in the above reaction contains 35% ammonia by volume. This mixture is cooled by refrigeration coils where ammonia gas changes to liquid ammonia at –33.4°C and is removed from the mixture. The other components of the mixture, hydrogen and nitrogen gases, are then recycled back into the reaction chamber.

Source of Nitrogen

One of the raw materials used for the production of ammonia is nitrogen gas and it is obtained by the fractional distillation of air. For this purpose, first of all carbon dioxide present in air is removed and the air is subjected to about 200 atmospheric pressure. This compressed air is then cooled and allowed to pass through a spiral jet. While escaping through this jet, the air suffers sudden expansion and its temperature is decreased. This process of compression and expansion is repeated again and again till the air is liquified. The liquid air is then fractionally distilled. Since the boiling point of nitrogen is less than oxygen, nitrogen evaporates first at -196°C leaving behind the oxygen. The separated nitrogen is reliquified and stored in specially designed cylinders.

Source of Hydrogen

The second raw material, hydrogen, is produced by heating methane in the limited amount of oxygen that is not enough to completely oxidize methane to carbon dioxide and water. With less oxygen available, the reaction products contain primarily hydrogen and carbon monoxide and a relatively small amount of carbon dioxide. The carbon monoxide obtained is then reacted with water to form carbon dioxide and more hydrogen gas.

Interesting information: 13% of total Nitrogen fixation in the environment is contributed by the Haber process.

🧠 Memorization & tips

📚 Teacher’s Lesson Planner

Session	Learning objectives	Activities & resources	Assessment
Day 1	Understand global importance of ammonia; introduce Haber process	Discuss fertilizers (80% use); show reaction N₂+3H₂⇌2NH₃; explain reversible nature	Oral quiz: why ammonia is crucial?
Day 2	Explain reaction conditions: temp, pressure, catalyst	Le Chatelier’s principle demo (simulation); effect of 200 atm and 400-500°C; role of Fe/Al₂O₃	Quick worksheet on condition effects
Day 3	Describe separation and recycling; source of N₂	Flowchart: reaction → cooling (-33.4°C) → liquid NH₃ removal; fractional distillation of air (b.p. -196°C)	Sketch the cycle with labels
Day 4	Source of hydrogen; overall industrial process	Methane + steam → CO + 3H₂; CO + H₂O → CO₂ + H₂; integration with Haber	Group discussion on raw material sustainability
Day 5	Review and formative quiz	Solve Quick Check 19.1; attempt 10 MCQs (integrated); discuss 13% fixation fact	MCQ quiz results & key analysis

⏱️ Each session ~40 min. Adjust based on class pace. Use @everexams.com quiz for instant feedback.

📝 Self check (10 MCQs)

Click on option — correct turns green, wrong turns red. Use submit to see score & key.