What NEET Asks
- Questions on Haber process conditions, catalysts, and equilibrium are frequently tested.
- Ammonia's structure, hybridization, and its basic nature are common conceptual questions.
- Expect problems involving ammonia's reactions with acids and metal ions, often in qualitative analysis.
Key Points
- Haber Process: N₂(g) + 3H₂(g) ⇌ 2NH₃(g), ΔH = -92.4 kJ/mol (exothermic, reversible).
- Optimal Conditions: Pressure ~200 atm, Temperature ~700 K (450-500 °C).
- Catalyst: Finely divided iron (Fe), with molybdenum (Mo) acting as a promoter.
- Structure: Pyramidal geometry, sp³ hybridization, bond angle ~107° due to lone pair repulsion.
- Properties: Colourless gas, pungent smell, highly soluble in water (forms NH₄OH, a weak base).
- Nature: Lewis base (due to lone pair donation), proton acceptor (Brønsted-Lowry base).
Must-Know Formula / Reaction
Haber's Process for Ammonia Synthesis: N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
- N₂: Nitrogen gas (reactant)
- H₂: Hydrogen gas (reactant)
- NH₃: Ammonia gas (product)
- ΔH = -92.4 kJ/mol: Indicates an exothermic reaction, releasing heat.
- Conditions: Catalyst (Fe/Mo), High Pressure (200 atm), Moderate Temperature (700 K).
Common Mistakes
- Students often confuse the theoretical thermodynamic conditions (low T, high P for max yield) with practical optimal conditions (moderate T for catalyst activity).
- Don't confuse the roles of iron (catalyst) and molybdenum (promoter); Fe speeds up the reaction, Mo enhances Fe's activity.
- Misinterpreting ammonia's basic nature; it's a base because of its lone pair of electrons, not the presence of hydroxide ions in its formula.
Rapid Revision
Ammonia (NH₃) is synthesized via the Haber process using N₂ and H₂ under specific conditions (Fe/Mo catalyst, ~200 atm, ~700 K). It has a pyramidal structure with sp³ hybridization due to a lone pair on nitrogen, making it a Lewis base and a key reagent in many reactions.