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ChemistryMediumClass 12
Nitrogen Compounds — NH₃, HNO₃, NO, NO₂
p-block Elements (Class 12 — Groups 15, 16, 17, 18)
10
JEE Qs
8%
Hard
75
min
Thoroughly memorize and understand the industrial preparations (Haber, Ostwald) including conditions and the comprehensive set of chemical reactions for NH₃, HNO₃, NO, and NO₂, paying special attention to redox behavior and complex formation.
🧮 Key Formulas
N₂(g) + 3H₂(g) ⇌ 2NH₃(g) (Haber process)
4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g) (Ostwald 1st step)
2NO(g) + O₂(g) → 2NO₂(g) (Ostwald 2nd step)
3NO₂(g) + H₂O(l) → 2HNO₃(aq) + NO(g) (Ostwald 3rd step)
NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH⁻(aq) (Basic nature of NH₃)
2NO₂(g) ⇌ N₂O₄(g) (Dimerization of NO₂)
✅ Key Points for JEE
- 1Master the conditions (catalyst, temperature, pressure) and principles (Le Chatelier's) for the Haber and Ostwald processes, as they are industrially significant and frequently tested.
- 2Understand ammonia (NH₃) as a Lewis base and its ability to form complex compounds with transition metal ions, leading to characteristic colored solutions.
- 3Nitric acid (HNO₃) acts as a strong oxidizing agent; learn the variable products (NO, NO₂, N₂O) formed with different metals and non-metals, depending on its concentration and temperature.
- 4Recognize the unique properties of nitrogen oxides: NO is paramagnetic and colorless, NO₂ is paramagnetic, reddish-brown, and dimerizes to diamagnetic N₂O₄, which is colorless. Be able to differentiate their reactions.
- 5Focus on the detailed reactions of each compound with various reagents, including acid-base reactions, redox reactions, and specific tests for identification.
⚠️ Common Mistakes
- ✕Confusing the products of nitric acid's reaction with metals based on its concentration (dilute vs. concentrated) and the reactivity of the metal.
- ✕Forgetting the specific catalysts and optimal conditions for the Haber and Ostwald processes, which are critical for yield and efficiency.
- ✕Misinterpreting the basicity of ammonia or its ability to form complexes, especially in qualitative analysis scenarios.
- ✕Not remembering the physical properties and interconversion reactions of NO and NO₂, particularly the dimerization of NO₂ to N₂O₄.
NCERT Chapters
- Class 12 Chemistry Part I Ch 7: The p-Block Elements (Group 15)