Comprehensive notes on Nitrogen (Group 15) and Sulfur (Group 16). Covers Ammonia (Haber Process), Nitric Acid (Ostwald Process), Sulfuric Acid (Contact Process), and Environmental issues like Acid Rain and Smog.
Inertness of Nitrogen: N2 is chemically unreactive due to the strong Triple Bond (N≡N, Bond Energy = 944 kJ/mol) and non-polar nature.
Ammonia (NH3): Prepared via Haber's Process (N2 + 3H2 ↔ 2NH3) at 400-450°C, 200 atm, Fe catalyst.
Oxides: N2O (Laughing gas), NO (Nitric oxide), NO2 (Reddish brown gas).
Ostwald's Process: Industrial preparation of HNO3.
1. Partial oxidation of NH3 to NO.
2. Oxidation of NO to NO2.
3. Absorption of NO2 in water to form HNO3.
Allotropes: Rhombic (Stable below 95.5°C) and Monoclinic (Stable above 95.5°C). Transition temperature is 95.5°C.
Structure: Crown shaped S8 molecules.
Steps:
1. Production of SO2: Burning S or FeS2.
2. Purification: Removal of Arsenic poison.
3. Contact Tower: 2SO2 + O2 ↔ 2SO3 (V2O5 catalyst, 450°C).
4. Absorption: SO3 + H2SO4 → H2S2O7 (Oleum).
5. Dilution: H2S2O7 + H2O → 2H2SO4.
Acid Rain: SO2 and NOx react with rain water to form H2SO4 and HNO3 (pH < 5.6).
Smog:
1. Classical Smog: Smoke + Fog + SO2 (Reducing).
2. Photochemical Smog: Hydrocarbons + NOx + Sunlight (Oxidizing, contains PAN).