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Environmental Chemistry CBSE Class 11 MCQ & Practice Questions

Practice Environmental Chemistry MCQs for CBSE Class 11 Chemistry with answers, explanations, chapter revision and related ChemNexa mock tests.

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Environmental Chemistry Revision Guide for CBSE Class 11 Chemistry

Environmental Chemistry is part of CBSE Class 11 Chemistry preparation. A strong revision plan should combine concept review with exam-style questions so that definitions, relationships, calculations and exceptions are recalled accurately.

Use the sample MCQs on this page to check understanding, then attempt the related ChemNexa tests for broader practice. When an answer is wrong, review the explanation and return to the underlying concept before attempting another set.

Important Topics

  • Core definitions and principles
  • Important equations or relationships
  • Common applications and examples
  • Frequently confused concepts
  • Exam-style multiple-choice questions
  • Error review and targeted revision

Revision Tip

Create a one-page summary of trends, structures, reactions, exceptions and key terminology for Environmental Chemistry, then test recall with mixed MCQs.

What to practise in Environmental Chemistry

Concept Revision

Revise definitions, principles, equations, trends and core ideas from Environmental Chemistry before attempting MCQs.

Exam-style MCQs

Use chapter-focused multiple-choice practice to improve accuracy, recall and application for CBSE Class 11 Chemistry.

Performance Practice

Attempt ChemNexa tests, review results and return to weak areas for another round of targeted revision.

Top 20 Environmental Chemistry MCQs with Answers

These public questions are selected from the exact Environmental Chemistry chapter, screened for topic relevance and deduplicated so repeated versions of the same MCQ are not shown publicly. Use them for quick revision, then sign in to attempt the complete test experience with more questions, results and performance review.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

1. The lowest layer of the atmosphere is:

  • A. Stratosphere
  • B. Troposphere
  • C. Mesosphere
  • D. Thermosphere
Answer: B
Explanation: The troposphere extends from Earth's surface to roughly 8–18 km and contains most atmospheric mass.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

2. The ozone layer is mainly located in the:

  • A. Troposphere
  • B. Stratosphere
  • C. Mesosphere
  • D. Exosphere
Answer: B
Explanation: Most atmospheric ozone is concentrated in the stratosphere.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

3. Which pollutant is a major cause of photochemical smog?

  • A. SO₂ only
  • B. NOₓ and hydrocarbons in sunlight
  • C. CO₂ only
  • D. N₂ only
Answer: B
Explanation: Nitrogen oxides and volatile hydrocarbons react under sunlight to form photochemical oxidants.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

4. The brownish component of photochemical smog is mainly:

  • A. NO₂
  • B. SO₃
  • C. NH₃
  • D. CO₂
Answer: A
Explanation: Nitrogen dioxide is a brown gas and an important smog component.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

5. PAN stands for:

  • A. Peroxyacetyl nitrate
  • B. Polyatomic aerosol nitrate
  • C. Primary atmospheric nitrogen
  • D. Peroxide acidic nitrate
Answer: A
Explanation: PAN is peroxyacetyl nitrate, a strong eye irritant in photochemical smog.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

6. Classical smog is associated mainly with:

  • A. Warm sunny weather
  • B. Cold humid conditions with SO₂ and smoke
  • C. Only ozone
  • D. Only methane
Answer: B
Explanation: Classical London-type smog forms in cold, foggy, sulfur-rich conditions.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

7. Acid rain generally has pH:

  • A. Greater than 7
  • B. Exactly 7
  • C. Below 5.6
  • D. Exactly 10
Answer: C
Explanation: Natural rain is mildly acidic; acid rain has pH below about 5.6.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

8. The main acids present in acid rain are:

  • A. HCl and HBr
  • B. H₂SO₄ and HNO₃
  • C. H₃PO₄ and H₂CO₃
  • D. H₂S and HCN
Answer: B
Explanation: Atmospheric SO₂ and NOₓ are oxidised to sulfuric and nitric acids.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

9. Which gas contributes most directly to formation of sulfuric acid in acid rain?

  • A. SO₂
  • B. CO
  • C. CH₄
  • D. NH₃
Answer: A
Explanation: SO₂ is oxidised to SO₃ and then hydrated to sulfuric acid.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

10. The greenhouse gas most associated with fossil-fuel combustion is:

  • A. CO₂
  • B. He
  • C. Ne
  • D. Ar
Answer: A
Explanation: Burning fossil fuels releases large quantities of carbon dioxide.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

11. Which gas has a much higher greenhouse-warming potential per molecule than CO₂?

  • A. Methane
  • B. Nitrogen
  • C. Oxygen
  • D. Hydrogen
Answer: A
Explanation: Methane absorbs infrared radiation strongly and has a higher warming potential per molecule.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

12. The enhanced greenhouse effect can lead to:

  • A. Global cooling only
  • B. Global warming and climate change
  • C. Ozone formation only
  • D. Lower sea level only
Answer: B
Explanation: Additional greenhouse gases trap more outgoing infrared radiation.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

13. Ozone depletion is primarily linked with:

  • A. CFCs
  • B. CO₂
  • C. O₂
  • D. N₂
Answer: A
Explanation: CFCs release chlorine radicals in the stratosphere that catalytically destroy ozone.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

14. A chlorine radical destroys ozone through a process that is:

  • A. Stoichiometric only
  • B. Catalytic
  • C. Neutralisation
  • D. Precipitation
Answer: B
Explanation: The chlorine radical is regenerated and can destroy many ozone molecules.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

15. The ozone hole is most pronounced over:

  • A. The equator
  • B. Antarctica
  • C. The Sahara
  • D. The Indian Ocean
Answer: B
Explanation: Polar stratospheric clouds and spring sunlight intensify ozone destruction over Antarctica.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

16. BOD is a measure of:

  • A. Total dissolved salts
  • B. Oxygen required by microbes to decompose organic matter
  • C. Acidity only
  • D. Heavy-metal concentration
Answer: B
Explanation: Biochemical oxygen demand estimates biodegradable organic pollution.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

17. A high BOD value generally indicates:

  • A. Very pure water
  • B. High organic pollution
  • C. No microbial activity
  • D. High salinity only
Answer: B
Explanation: More biodegradable matter requires more oxygen for microbial decomposition.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

18. Eutrophication is caused mainly by excess:

  • A. Nitrates and phosphates
  • B. Oxygen and nitrogen gas
  • C. Sand
  • D. Sodium chloride only
Answer: A
Explanation: Nutrient enrichment promotes algal blooms and oxygen depletion.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

19. Which process often follows eutrophication?

  • A. Increase in dissolved oxygen permanently
  • B. Algal bloom followed by oxygen depletion
  • C. Immediate desalination
  • D. Ozone formation
Answer: B
Explanation: Decay of excessive algae consumes dissolved oxygen and harms aquatic life.

CBSE Class 11 Chemistry · Environmental Chemistry · Very Very Hard

20. Biomagnification refers to:

  • A. Dilution of pollutants up a food chain
  • B. Increasing pollutant concentration at higher trophic levels
  • C. Breakdown of plastics
  • D. Removal of metals from water
Answer: B
Explanation: Persistent pollutants accumulate progressively in organisms at higher trophic levels.

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Environmental Chemistry Practice Tests

Environmental Chemistry Frequently Asked Questions

How should I prepare Environmental Chemistry for CBSE Class 11 Chemistry?

Revise the core concepts first, make a short list of important relationships or exceptions, and then solve chapter-focused MCQs while reviewing every error.

How can ChemNexa help with Environmental Chemistry practice?

This page provides public sample questions and links to published ChemNexa tests so you can combine quick revision with structured practice.

What should I do after getting an MCQ wrong?

Identify whether the mistake came from a concept gap, calculation, unit, sign, wording or memory error, review that point, and then attempt a similar question again.

Continue with another chapter to build connected concepts and strengthen your overall Chemistry preparation.

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