N

Nitrogen Fixation

N₂ + 3H₂ → 2NH₃ (Haber process); biological: N₂ + 8H⁺ + 8e⁻ → 2NH₃+H₂ (nitrogenase)
Quick Reference
Formula / NotationN₂ + 3H₂ → 2NH₃ (Haber process); biological: N₂ + 8H⁺ + 8e⁻ → 2NH₃+H₂ (nitrogenase)
Also Known AsHaber process, biological nitrogen fixation, N₂ reduction, nitrogen fixation

What is Nitrogen Fixation?

The conversion of atmospheric nitrogen (N₂) into compounds usable by organisms, such as ammonia or nitrates. Biological fixation occurs through bacteria like Rhizobium. Industrial fixation uses the Haber process. Fixed nitrogen is essential for protein and nucleic acid synthesis.

Formula & Notation

N₂ + 3H₂ → 2NH₃ (Haber process); biological: N₂ + 8H⁺ + 8e⁻ → 2NH₃+H₂ (nitrogenase)

Other Names / Synonyms: Haber process, biological nitrogen fixation, N₂ reduction, nitrogen fixation

Properties & Characteristics

Nitrogen fixation is the conversion of atmospheric dinitrogen (N₂) into reactive nitrogen compounds (NH₃, NO₃⁻, N₂O) that can be utilised by living organisms. Industrial nitrogen fixation: Haber process (N₂ + 3H₂ → 2NH₃, Fe catalyst, 400-500°C, 150-300 atm). Biological nitrogen fixation: carried out by nitrogenase enzyme complexes in certain bacteria (Rhizobium, Azotobacter, cyanobacteria), requiring 16 ATP per N₂ reduced. The N₂ triple bond (945 kJ/mol) makes fixation energetically demanding.

Uses & Applications

Nitrogen fixation is essential to global food security: ~50% of the world's protein nitrogen is derived from Haber process ammonia (fertilisers). Biological N-fixation in legume root nodules reduces dependence on synthetic fertilisers. Fixed nitrogen is the starting material for all nitrogen-containing chemicals: fertilisers, explosives, pharmaceuticals, dyes.

Safety Information

The Haber process operates under extreme conditions (400-500°C, 150-300 atm) — high-pressure reactor engineering and safety systems are critical. NH₃ is toxic (TLV = 25 ppm), flammable (15-28% in air), and corrosive. Liquid ammonia leaks are a major industrial hazard requiring gas detection and emergency procedures.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Nitrogen Fixation
Formula N₂ + 3H₂ → 2NH₃ (Haber process); biological: N₂ + 8H⁺ + 8e⁻ → 2NH₃+H₂ (nitrogenase)
Synonyms Haber process, biological nitrogen fixation, N₂ reduction, nitrogen fixation

Frequently Asked Questions

The conversion of atmospheric nitrogen (N₂) into compounds usable by organisms, such as ammonia or nitrates. Biological fixation occurs through bacteria like Rhizobium. Industrial fixation uses the Haber process. Fixed nitrogen is essential for protein and nucleic acid synthesis.

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