EAPCET Chemistry · Intermediate first year
Environmental Chemistry
Environmental Chemistry covers atmospheric, water and soil pollution, the greenhouse effect, ozone depletion, acid rain and green chemistry.
- Subject
- Chemistry
- Taught in
- Intermediate first year
- Chemistry in the paper
- 40 of 160 questions
Key formulas and results
- Greenhouse gases include CO₂, CH₄, N₂O, CFCs and water vapour
- CFCs deplete ozone through chlorine radicals
- Acid rain has pH below 5.6
- Classical smog is reducing; photochemical smog is oxidising
- Clean water has a BOD below about 5 ppm
What this chapter covers
- Atmospheric pollution
- Greenhouse effect
- Ozone depletion
- Acid rain
- Smog
- Water pollution and green chemistry
How it is usually asked
- Pollutants and their effects
- Types of smog
- Ozone chemistry
- Water quality
Understanding Environmental Chemistry
Environmental chemistry studies how chemicals move through and harm the air, water and soil. In the troposphere, the main pollutants are oxides of sulphur, nitrogen and carbon, hydrocarbons and particulates. Carbon monoxide is dangerous because it binds haemoglobin far more strongly than oxygen, forming carboxyhaemoglobin. Gases such as CO₂, CH₄, N₂O, CFCs and water vapour trap outgoing infrared radiation, causing the greenhouse effect and global warming.
Normal rain is slightly acidic (pH about 5.6) because dissolved CO₂ forms carbonic acid; acid rain, with pH below 5.6, comes from SO₂ and NO₂ forming H₂SO₄ and HNO₃. Classical smog forms in cool, humid air from smoke, fog and SO₂ and is reducing. Photochemical smog forms in warm, sunny weather when NOₓ and hydrocarbons react in sunlight to give ozone, PAN, acrolein and formaldehyde, and it is oxidising.
In the stratosphere, CFCs release chlorine radicals that destroy ozone in a chain: Cl• + O₃ → ClO• + O₂. Water pollution is measured by BOD; clean water has a BOD below about 5 ppm. Excess fluoride causes mottling of teeth, and excess nitrate causes blue-baby syndrome. Green chemistry aims to prevent pollution at the source, for example dry cleaning with liquid CO₂ and bleaching paper with H₂O₂ instead of chlorine.
Worked example
EAPCET-style question
Which of the following is a characteristic constituent of classical (London) smog rather than photochemical smog?
- (1)Ozone
- (2)Peroxyacetyl nitrate (PAN)
- (3)Sulphur dioxide
- (4)Formaldehyde
Solution
- Classical smog is a mixture of smoke, fog and sulphur dioxide formed in cool, humid weather; it is reducing in nature.
- Photochemical smog forms when nitrogen oxides and hydrocarbons react in sunlight.
- Its products are ozone, PAN, acrolein and formaldehyde, and it is oxidising in nature.
- So ozone, PAN and formaldehyde belong to photochemical smog, and sulphur dioxide is the marker of classical smog.
Answer: Sulphur dioxide
Common mistakes to avoid
- Calling photochemical smog reducing — it is oxidising (O₃, PAN), while classical smog with SO₂ is reducing.
- Taking pH 7 as the boundary for acid rain — normal rain is already about 5.6, and acid rain is below that.
- Thinking ozone depletion and the greenhouse effect are the same problem — ozone loss lets in more UV radiation, while greenhouse gases trap infrared and warm the Earth.
- Reading a high BOD as clean water — a high BOD means more organic matter and more pollution.
How to prepare it
Entirely factual — a list-based revision is the fastest way to secure these marks.
Once the formulas feel familiar, test them the way the exam does: practise Environmental Chemistry questions chapter-wise, then attempt a full previous year paper to see whether it holds up under a 3-hour timer.
Related Chemistry chapters
- p-Block Elements – Group 14 (Carbon Family)Intermediate first year
- Organic ChemistryIntermediate first year
See every chapter in the EAPCET Chemistry syllabus.
Practise Environmental Chemistry chapter-wise
Chapter-wise quizzes show exactly which topics in this chapter you still get wrong — before a full paper does.
Frequently asked questions
- Is Environmental Chemistry part of the EAPCET Chemistry syllabus?
- Yes. Environmental Chemistry is taught in Intermediate first year Chemistry, and the EAPCET Engineering syllabus is based on the Intermediate first- and second-year syllabus. Check the official notification each year for any changes.
- How should I prepare Environmental Chemistry for EAPCET?
- Entirely factual — a list-based revision is the fastest way to secure these marks.
- How many Chemistry questions are there in EAPCET?
- 40 of the 160 questions in the Engineering paper are Chemistry, spread across 24 chapters.
- What mistakes do students make in Environmental Chemistry?
- Calling photochemical smog reducing — it is oxidising (O₃, PAN), while classical smog with SO₂ is reducing. Taking pH 7 as the boundary for acid rain — normal rain is already about 5.6, and acid rain is below that. Thinking ozone depletion and the greenhouse effect are the same problem — ozone loss lets in more UV radiation, while greenhouse gases trap infrared and warm the Earth. Reading a high BOD as clean water — a high BOD means more organic matter and more pollution.