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🧪 Chemistry  ·  Environmental Chemistry  ·  NEET & JEE

Eutrophication of a lake is caused by an excess of:

Answer: nitrates and phosphates.

  • A dissolved oxygen
  • B nitrates and phosphates
  • C strong mineral acids
  • D dissolved heavy metals

Correct answer: B. nitrates and phosphates

Explanation: Nutrient enrichment triggers algal blooms; their decay depletes oxygen and harms aquatic life.

Classical (London) SmogSources: coal burningSO₂ + particulates + fogReducing typeConditions: cold, humid,early morning, winterVisibility: very low (fog)London, 1952 - ~4000 deathsHarms: eyes, lungs, bronchitisPhotochemical (LA) SmogSources: vehicles, industriesNOx + hydrocarbons + UVOxidising typeConditions: warm, sunny,afternoon, summerProducts: O₃, PAN, acroleinLos Angeles (common in cities)Harms: eyes, rubber cracking

Classical smog is a reducing mixture of SO₂ and fog, while photochemical smog is an oxidising mixture generated by UV-driven reactions of NOx and hydrocarbons.

Concept context

Understand how human activities alter the atmosphere, water, and soil. Covers air pollutants, smog types, ozone depletion, acid rain, greenhouse effect, water and soil pollution, and the principles of green chemistry.

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