Comprehensive notes on Environmental Chemistry, covering Layers of Atmosphere, Ozone Depletion (CFCs), Global Warming, Acid Rain, and Smog (Photochemical vs Industrial).
1. Troposphere (0-12 km): Temperature decreases (17°C to -58°C). Contains 75% mass of atmosphere and weather phenomena.
2. Stratosphere (12-50 km): Temperature increases (-58°C to -2°C). Presence of Ozone Layer (absorbs UV).
3. Mesosphere (50-85 km): Temperature decreases (Coldest layer, -93°C).
4. Thermosphere (85-500 km): Temperature increases drastically (Ionization occurs).
Role of CFCs: Chlorofluorocarbons release Chlorine free radicals (Cl•) in Stratosphere.
Reactions:
1. Cl• + O3 → ClO• + O2
2. ClO• + O → Cl• + O2
The Chlorine radical is regenerated, destroying thousands of Ozone molecules (Chain Reaction).
Definition: Rain water having pH less than 5.6.
Causes: SO2 and NOx dissolve in rain to form acids.
1. 2SO2 + O2 + 2H2O → 2H2SO4 (Sulfuric Acid)
2. 4NO2 + 2H2O + O2 → 4HNO3 (Nitric Acid)
Effects: Erodes marble (CaCO3), damages aquatic life, leaches heavy metals.
1. Classical Smog (London Smog): Smoke + Fog + SO2. Reducing in nature. Occurs in humid, cool climates.
2. Photochemical Smog (Los Angeles Smog): Hydrocarbons + NOx + Sunlight. Oxidizing in nature (contains Ozone, PAN). Occurs in dry, sunny climates.
Mechanism: Green House Gases (CO2, CH4, H2O) allow short-wave solar radiation to enter but trap long-wave infrared radiation emitted by Earth.
Effects: Rise in Earth's temperature (Global Warming), melting of ice caps, sea-level rise.