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Environmental chemistry
Chemistry
Useful for: OSSC RHT — Regular High School Teacher, OSEPA Upper Primary — Science, OSSC Science, OSSSC Govt TGT Science — CBZ, OSSSC Govt TGT Science — PCM, SSB Lecturer (Degree Colleges), SSB TGT CBZ, SSB TGT PCM
Overview
Environmental chemistry studies chemical processes in air, water and soil, including pollution and its control.
Key points
- Acid rain has pH below 5.6, caused by sulphur and nitrogen oxides.
- CFCs release chlorine radicals that destroy stratospheric ozone.
- Photochemical smog forms from NOx and hydrocarbons in sunlight, producing ozone and PAN.
- Greenhouse gases trap heat and warm the Earth.
- High BOD indicates organic pollution in water.
- Green chemistry (Anastas and Warner) has 12 principles for safer processes.
Explanation
- Eutrophication follows nutrient overload.
- Heavy metals (mercury, lead) bioaccumulate.
- Catalytic converters reduce vehicle emissions.
- Ground-level ozone is harmful; stratospheric ozone is protective.
- The Montreal Protocol phased out CFCs.
Step by step
- Identify the concept, method or fact asked.
- Recall the definition, thinker, year or rule.
- Apply it and eliminate extreme or mismatched options.
Examples
- Marble monuments corroding → acid rain.
- Ozone hole over Antarctica → CFCs.
- Brown haze in cities on sunny days → photochemical smog.
Traps and advanced points
- Trap: Calling all ozone harmful.
- Trap: Wrong acid-rain pH.
- Trap: Mixing BOD meaning.
Quick revision
- Acid rain < 5.6.
- CFC → ozone depletion.
- Green chemistry 12 principles.
Practice MCQs
Acid rain has a pH below —
- 5.6
- 4
- 8
- 7
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Answer: (a) 5.6. Below 5.6.
Acid rain is mainly caused by oxides of —
- oxygen
- helium
- sulphur and nitrogen
- carbon only
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Answer: (c) sulphur and nitrogen. SO₂ and NOx.
Stratospheric ozone is destroyed mainly by —
- CFCs
- oxygen
- nitrogen
- water vapour
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Answer: (a) CFCs. Chlorine radicals from CFCs.
Photochemical smog forms from NOx and hydrocarbons in —
- snow
- rain only
- darkness
- sunlight
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Answer: (d) sunlight. Sunlight drives the reactions.
High BOD in water indicates —
- salinity
- clean water
- organic pollution
- high oxygen
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Answer: (c) organic pollution. Microbes use more oxygen.
Green chemistry has how many principles (Anastas and Warner)?
- 15
- 8
- 10
- 12
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Answer: (d) 12. 12 principles.
Excess nutrients causing algal bloom is —
- eutrophication
- biomagnification
- desertification
- smog
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Answer: (a) eutrophication. Nutrient overload.
Ground-level ozone is —
- harmful
- harmless always
- a fertiliser
- protective
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Answer: (a) harmful. It is a pollutant.
The Montreal Protocol phased out —
- lead
- CFCs
- carbon dioxide
- plastics
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Answer: (b) CFCs. Ozone-depleting substances.
Catalytic converters in vehicles reduce —
- fuel efficiency only
- tyre wear
- noise only
- harmful exhaust gases
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Answer: (d) harmful exhaust gases. They convert CO, NOx and hydrocarbons.
More topics in this chapter
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