Ch 14 covers the chemical aspects of environmental pollution — air, water, and soil pollution, their causes, effects, and remedies, along with the principles of green chemistry.
Primary pollutants: CO (incomplete combustion), SO₂ (coal), NOₓ (vehicle exhaust), hydrocarbons, particulates. Photochemical smog: NO₂ + UV → O₃ + PAN (peroxyacetylnitrate) — irritates eyes, damages plants. Acid rain: SO₂ + H₂O → H₂SO₃; NOₓ + H₂O → HNO₃ — damages buildings, kills fish, acidifies soil. Greenhouse effect: CO₂, CH₄, N₂O trap IR radiation → global warming.
Water pollution: domestic sewage (pathogens, BOD), industrial effluents (heavy metals, organic chemicals), agricultural runoff (fertilisers → eutrophication, pesticides → biomagnification). BOD: biological oxygen demand — high BOD = polluted water. Soil pollution: pesticides, industrial waste, landfills. Green chemistry: designing processes that reduce/eliminate hazardous substances (atom economy, safer solvents).
Download: https://ncert.nic.in/textbook/pdf/kech207.pdf | Part II: https://ncert.nic.in/textbook/pdf/kech2ps.zip
BOD (Biological Oxygen Demand) is the amount of dissolved oxygen needed by microorganisms to decompose organic matter in water. High BOD indicates heavily polluted water (lots of organic waste). When BOD is high, dissolved oxygen drops, killing fish and other aquatic organisms. Clean water has BOD < 5 mg/L; polluted water can have BOD > 100 mg/L.
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