Environmental Effects of Organic Compounds MCQs – Class 11
Environmental Effects of Organic Compounds MCQs – Class 11 Chemistry
Course: CBSE Class 11 Chemistry – MCQs with Answers and Explanations
Section: Organic Chemistry – MCQ Titles
The following 50 Multiple Choice Questions (MCQs) are strictly aligned with the NCERT chapter “Environmental Chemistry” and the organic-chemistry–related environmental effects discussed at the Class 11 level. The questions are arranged section-wise with clear, concept-clearing explanations, making them ideal for CBSE Class 11 board exam preparation.
Section A: Organic Compounds and Environment
1. Environmental effects of organic compounds mainly arise due to
A. their colour
B. their reactivity and persistence
C. their taste
D. their molecular mass
Answer: B
Explanation: Many organic compounds are reactive or persistent, leading to pollution and ecological damage.
2. Which of the following organic compounds is a major air pollutant?
A. Methane
B. Benzene
C. Ethanol
D. Acetic acid
Answer: B
Explanation: Benzene is toxic and carcinogenic, causing air pollution.
3. Organic pollutants that persist for long periods are called
A. biodegradable pollutants
B. persistent organic pollutants
C. primary pollutants
D. temporary pollutants
Answer: B
Explanation: POPs remain in the environment for long durations.
Section B: Hydrocarbons and Air Pollution
4. Incomplete combustion of hydrocarbons produces
A. CO₂ and H₂O
B. CO and soot
C. nitrogen oxides
D. ozone
Answer: B
Explanation: Lack of oxygen leads to CO and carbon particles.
5. Carbon monoxide is harmful because it
A. increases global warming
B. forms acids in air
C. reduces oxygen transport in blood
D. destroys ozone layer
Answer: C
Explanation: CO binds with haemoglobin, reducing oxygen supply.
6. Which hydrocarbon contributes most to photochemical smog?
A. Methane
B. Ethyne
C. Unsaturated hydrocarbons
D. Saturated hydrocarbons
Answer: C
Explanation: Alkenes and aromatics react with NOₓ in sunlight.
7. Photochemical smog is formed in presence of
A. rain and fog
B. sunlight and hydrocarbons
C. wind and dust
D. ozone only
Answer: B
Explanation: Sunlight initiates reactions between NOₓ and hydrocarbons.
Section C: Aromatic Compounds and Health Hazards
8. Benzene exposure mainly affects
A. lungs
B. liver
C. bone marrow
D. kidneys
Answer: C
Explanation: Benzene is carcinogenic and affects blood-forming tissues.
9. Polycyclic aromatic hydrocarbons (PAHs) are released during
A. fermentation
B. complete combustion
C. incomplete combustion
D. electrolysis
Answer: C
Explanation: PAHs form during incomplete burning of organic matter.
10. PAHs are considered dangerous because they are
A. biodegradable
B. volatile
C. carcinogenic
D. non-reactive
Answer: C
Explanation: Many PAHs cause cancer.
Section D: Chlorinated Organic Compounds
11. Which compound is responsible for ozone depletion?
A. Methane
B. Chloroform
C. Chlorofluorocarbons (CFCs)
D. Ethanol
Answer: C
Explanation: CFCs release chlorine radicals that destroy ozone.
12. CFCs were widely used as
A. fuels
B. refrigerants
C. fertilisers
D. pesticides
Answer: B
Explanation: CFCs were common in refrigerators and air conditioners.
13. The harmful effect of ozone depletion is
A. acid rain
B. increased UV radiation
C. global cooling
D. smog formation
Answer: B
Explanation: UV rays cause skin cancer and crop damage.
Section E: Organic Pesticides and Insecticides
14. DDT belongs to the class of
A. biodegradable pesticides
B. organophosphates
C. chlorinated hydrocarbons
D. carbamates
Answer: C
Explanation: DDT is a chlorinated organic pesticide.
15. Excessive use of DDT leads to
A. eutrophication
B. bioaccumulation
C. water hardness
D. ozone formation
Answer: B
Explanation: DDT accumulates in the food chain.
16. Bioaccumulation means
A. rapid degradation
B. accumulation in soil
C. build-up of substances in organisms
D. conversion to harmless products
Answer: C
Explanation: Persistent compounds concentrate at higher trophic levels.
17. Which effect of pesticides is seen in birds?
A. increased fertility
B. thinning of eggshells
C. increased lifespan
D. improved immunity
Answer: B
Explanation: DDT weakens eggshells, reducing bird populations.
Section F: Detergents and Water Pollution
18. Synthetic detergents cause water pollution mainly due to
A. pleasant smell
B. foam formation
C. acidity
D. hardness
Answer: B
Explanation: Excess foam reduces oxygen exchange.
19. Non-biodegradable detergents contain
A. straight-chain hydrocarbons
B. branched-chain hydrocarbons
C. alcohols
D. esters
Answer: B
Explanation: Branched chains resist microbial degradation.
20. Eutrophication results from excessive presence of
A. hydrocarbons
B. phosphates and nitrates
C. heavy metals
D. plastics
Answer: B
Explanation: Nutrient enrichment promotes algal blooms.
Section G: Plastics and Polymers
21. Plastics are environmental hazards because they are
A. expensive
B. biodegradable
C. non-biodegradable
D. soluble in water
Answer: C
Explanation: Plastics persist for long periods.
22. Which polymer is biodegradable?
A. PVC
B. Polythene
C. Nylon-6,6
D. PHBV
Answer: D
Explanation: PHBV is a biodegradable polymer.
23. Burning plastics releases
A. oxygen
B. harmless gases
C. toxic gases like HCl
D. nitrogen
Answer: C
Explanation: PVC releases HCl and other toxic fumes.
Section H: Organic Solvents and Industrial Waste
24. Organic solvents mainly pollute
A. soil only
B. air and water
C. rocks
D. atmosphere only
Answer: B
Explanation: Solvents evaporate and also contaminate water.
25. Which solvent is highly toxic and carcinogenic?
A. Ethanol
B. Acetone
C. Benzene
D. Ether
Answer: C
Explanation: Benzene is highly harmful.
26. Volatile organic compounds (VOCs) mainly cause
A. acid rain
B. photochemical smog
C. ozone depletion only
D. water hardness
Answer: B
Explanation: VOCs react with NOₓ under sunlight.
Section I: Organic Compounds and Global Issues
27. Methane contributes to
A. ozone depletion
B. acid rain
C. greenhouse effect
D. smog only
Answer: C
Explanation: Methane is a potent greenhouse gas.
28. Greenhouse gases trap
A. UV radiation
B. visible light
C. infrared radiation
D. X-rays
Answer: C
Explanation: Trapping IR radiation causes global warming.
29. Which organic compound has high global warming potential?
A. Methanol
B. Ethanol
C. Methane
D. Acetic acid
Answer: C
Explanation: Methane traps more heat than CO₂ per molecule.
Section J: Green Chemistry and Environmental Protection
30. Green chemistry aims to
A. increase chemical waste
B. use renewable raw materials
C. promote toxic reagents
D. increase pollution
Answer: B
Explanation: Green chemistry reduces environmental impact.
31. Which process follows green chemistry principles?
A. Burning plastics
B. Using CFCs
C. Catalytic reactions
D. Excessive pesticide use
Answer: C
Explanation: Catalysts reduce waste and energy use.
Section K: Conceptual NCERT-Based MCQs
32. Organic pollutants are more dangerous when they are
A. water soluble
B. biodegradable
C. persistent and fat-soluble
D. volatile
Answer: C
Explanation: Fat-soluble pollutants bioaccumulate.
33. Which of the following is a secondary pollutant?
A. Methane
B. Benzene
C. Ozone
D. Ethanol
Answer: C
Explanation: Ozone forms from reactions of organic compounds and NOₓ.
34. Organic compounds cause water pollution mainly by
A. increasing hardness
B. reducing dissolved oxygen
C. increasing density
D. changing colour only
Answer: B
Explanation: Decomposition consumes oxygen.
Section L: Application-Based MCQs
35. Which organic compound is used as fuel but also causes pollution?
A. Ethanol
B. Methane
C. Biogas
D. Hydrogen
Answer: B
Explanation: Methane is useful but contributes to greenhouse effect.
36. Oil spills mainly consist of
A. inorganic salts
B. hydrocarbons
C. carbohydrates
D. proteins
Answer: B
Explanation: Petroleum hydrocarbons pollute marine life.
37. Detergent pollution can be reduced by using
A. more detergents
B. branched detergents
C. biodegradable detergents
D. concentrated detergents
Answer: C
Explanation: Biodegradable detergents decompose easily.
Section M: High-Order Thinking MCQs
38. Which property of organic compounds increases environmental risk?
A. Low reactivity
B. High biodegradability
C. Chemical stability
D. Low molecular mass
Answer: C
Explanation: Stable compounds persist in environment.
39. Organic pesticides are being replaced because they
A. are ineffective
B. are expensive
C. accumulate in food chains
D. evaporate easily
Answer: C
Explanation: Bioaccumulation harms ecosystems.
40. The best solution to organic pollution is
A. dilution
B. incineration
C. prevention at source
D. dumping in landfills
Answer: C
Explanation: Preventing pollutant formation is most effective.
Section N: Final Conceptual MCQs
41. Which organic compound is least harmful to environment?
A. DDT
B. Benzene
C. Ethanol
D. CFC-12
Answer: C
Explanation: Ethanol is biodegradable.
42. Organic compounds mainly enter water bodies through
A. rainfall
B. industrial effluents
C. condensation
D. evaporation
Answer: B
Explanation: Industrial discharge is a major source.
43. Which factor increases toxicity of organic compounds?
A. biodegradability
B. persistence
C. low solubility
D. low boiling point
Answer: B
Explanation: Persistent compounds remain longer in environment.
44. Which of the following promotes sustainable development?
A. Excessive pesticide use
B. Green chemistry
C. Plastic disposal
D. Fossil fuel burning
Answer: B
Explanation: Green chemistry minimises environmental harm.
45. Organic waste is less harmful when it is
A. persistent
B. non-biodegradable
C. biodegradable
D. aromatic
Answer: C
Explanation: Biodegradable waste decomposes naturally.
46. Which organic compound contributes to indoor air pollution?
A. Methane
B. Formaldehyde
C. Acetone
D. Ethanol
Answer: B
Explanation: Formaldehyde is released from paints and furniture.
47. Which of the following is a major source of VOCs?
A. Trees
B. Automobiles
C. Rivers
D. Rocks
Answer: B
Explanation: Vehicle exhaust releases VOCs.
48. Bioaccumulation is maximum in
A. producers
B. primary consumers
C. secondary consumers
D. top consumers
Answer: D
Explanation: Pollutants concentrate at higher trophic levels.
49. Organic pollution mainly affects
A. atmosphere only
B. hydrosphere only
C. biosphere
D. lithosphere only
Answer: C
Explanation: Living organisms are directly impacted.
50. Study of environmental effects of organic compounds helps in
A. increasing production
B. understanding pollution control
C. synthesising more chemicals
D. promoting waste
Answer: B
Explanation: It aids in designing safer chemicals and control strategies.
✅ Completion Note
This completes a fully NCERT-aligned, CBSE-standard set of 50 MCQs on Environmental Effects of Organic Compounds, ideal for concept clarity, revision, and exam-focused preparation.