RPSC 1st Grade Chemistry: Environmental Pollution, Ozone & Greenhouse Effect (Full Notes, Tips & Tricks) प्रथम श्रेणी रसायन व्याख्याता नोट्स

Environment Pollution Ozone Depletion And Greenhouse Effect For RPSC School Lecturer Exam

1. Introduction to Environmental Pollution

Environmental pollution refers to undesirable changes in the physical, chemical, and biological characteristics of the environment that adversely affect living organisms and natural systems.

Types of Pollution

Type	Major Pollutants	Source
Air Pollution	CO₂, SO₂, NOₓ, CFCs	Industries, vehicles
Water Pollution	Heavy metals, sewage	Industrial discharge
Soil Pollution	Pesticides, plastics	Agriculture
Thermal Pollution	Heated water	Power plants
Radioactive Pollution	Nuclear waste	Nuclear plants

Exam Tip: Focus on mechanism-based questions, atmospheric layers, and international protocols.

2. Structure of Atmosphere

Layer	Height	Importance
Troposphere	0–12 km	Weather and pollution
Stratosphere	12–50 km	Ozone layer present
Mesosphere	50–80 km	Meteor burning
Thermosphere	>80 km	Ionosphere

Key Point: Ozone layer exists between 15–35 km in the stratosphere.

3. Ozone Layer

Ozone (O₃) is a triatomic molecule of oxygen that absorbs harmful ultraviolet radiation.

Formation of Ozone (Chapman Cycle)

O₂ + hv → O + O
O + O₂ → O₃
O₃ + hv → O₂ + O

Ozone formation and destruction occur in natural equilibrium.

4. Ozone Depletion

Ozone depletion is the reduction in ozone concentration in the stratosphere, allowing more UV radiation to reach Earth.

Main Cause: CFCs

CFCl₃ (Freon-11)
CF₂Cl₂ (Freon-12)

Mechanism

CFCl₃ → CFCl₂ + Cl• (UV radiation)
Cl• + O₃ → ClO• + O₂
ClO• + O → Cl• + O₂

Net Reaction: O₃ + O → 2O₂

One chlorine radical can destroy nearly 100,000 ozone molecules.

Exam Trick: Catalyst in ozone depletion → Cl• radical

5. Ozone Hole

Ozone hole refers to severe depletion over Antarctica.

Reason	Explanation
Low Temperature	Formation of Polar Stratospheric Clouds
PSC Role	Convert inactive chlorine to active form
Sunlight Return	Triggers ozone destruction

Reaction on PSC surface:

ClONO₂ + HCl → Cl₂ + HNO₃

Cl₂ → 2Cl• (UV radiation)

6. Effects of Ozone Depletion

Human Health: Skin cancer, cataracts
Plants: Reduced photosynthesis
Marine Life: Damage to phytoplankton
Materials: Plastic degradation

7. Control Measures

Montreal Protocol (1987)
Use of HFCs instead of CFCs
Reduced aerosol usage

Montreal Protocol → Ozone protection

8. Greenhouse Effect

Greenhouse effect is the warming of Earth's surface due to trapping of infrared radiation by greenhouse gases.

Without greenhouse effect: Temperature would be -18°C

Mechanism

Solar radiation enters Earth
Earth emits infrared radiation
Greenhouse gases absorb IR radiation

Greenhouse Gases

Gas	Contribution	Source
CO₂	~60%	Fossil fuels
CH₄	~20%	Cattle, rice fields
N₂O	~6%	Fertilizers
CFCs	~10%	Refrigerants

Greenhouse gases absorb infrared radiation, not UV.

9. Greenhouse Effect vs Ozone Depletion

Feature	Greenhouse Effect	Ozone Depletion
Layer	Troposphere	Stratosphere
Radiation	Infrared	Ultraviolet
Main Cause	CO₂, CH₄	CFCs
Result	Warming	UV increase

Ozone depletion is not the same as global warming.

10. Enhanced Greenhouse Effect

Burning fossil fuels
Deforestation
Industrial emissions
Agriculture (methane)

CO₂ increased from 280 ppm to ~420 ppm.

11. Consequences

Temperature rise
Glacier melting
Climate change
Ecosystem disruption

12. Control Measures

Renewable energy
Afforestation
Energy efficiency
Paris Agreement

Paris Agreement → Climate change control

Quick Revision Points

Ozone layer protects from UV radiation
CFCs cause ozone depletion
Cl radical acts as catalyst
Greenhouse gases trap infrared radiation
CO₂ is the major contributor

Expected RPSC Questions

Explain Chapman cycle
Mechanism of ozone depletion
Greenhouse effect explanation
Difference between ozone depletion and global warming

Global Warming, Climate Change And Advanced Concepts

1. Global Warming

Global warming refers to the long-term increase in Earth’s average surface temperature due to the enhanced greenhouse effect caused by human activities.

Global warming is a consequence of the enhanced greenhouse effect, not a separate phenomenon.

Scientific Evidence

Increase in global average temperature (~1.1°C since pre-industrial era)
Rising CO₂ concentration (~420 ppm)
Melting glaciers and polar ice
Rising sea levels

2. Sources of Global Warming

Source	Gas Emitted	Process
Fossil fuel combustion	CO₂	Oxidation of carbon
Agriculture	CH₄	Anaerobic decomposition
Fertilizers	N₂O	Nitrification & denitrification
Deforestation	CO₂	Reduced carbon absorption

3. Global Warming Potential (GWP)

GWP measures the heat trapping ability of a gas compared to CO₂.

Gas	GWP (100 years)
CO₂	1
CH₄	28–36
N₂O	265–298
CFCs	Up to 10,000+

Highest GWP → CFCs (very important MCQ)

4. Carbon Cycle

The carbon cycle is the biogeochemical cycle through which carbon is exchanged between atmosphere, hydrosphere, biosphere, and geosphere.

Main Processes

Photosynthesis: CO₂ → Organic matter
Respiration: Organic matter → CO₂
Combustion: Fossil fuels → CO₂
Ocean absorption: CO₂ dissolves in seawater

Human activities disturb the natural carbon balance, increasing atmospheric CO₂.

5. Climate Change

Climate change refers to long-term alterations in temperature, precipitation, and weather patterns.

Difference Between Weather And Climate

Weather	Climate
Short-term	Long-term
Local	Global
Highly variable	Relatively stable trends

6. Feedback Mechanisms

1. Positive Feedback

Ice melts → reduces albedo → more heat absorption → more melting

2. Negative Feedback

Increased CO₂ → increased plant growth → more CO₂ absorption

Positive feedback amplifies warming (very important concept)

7. Effects of Global Warming

Sea level rise due to glacier melting
Extreme weather events (floods, droughts)
Loss of biodiversity
Ocean acidification

Ocean Acidification Reaction

CO₂ + H₂O → H₂CO₃ (carbonic acid)

8. (RPSC Important)

Impact	Region
Glacier retreat	Himalayas
Heat waves	Rajasthan
Floods	Assam, Bihar
Sea level rise	Coastal areas

Rajasthan frequently experiences heat waves due to climate change.

9. Mitigation Strategies

Switch to renewable energy
Carbon capture and storage (CCS)
Energy efficiency
Afforestation and reforestation

10. Adaptation Strategies

Climate-resilient agriculture
Water conservation
Disaster management systems
Urban planning

11. International Agreements

Agreement	Year	Purpose
Kyoto Protocol	1997	Reduce GHG emissions
Paris Agreement	2015	Limit temperature rise below 2°C

Paris Agreement target: Limit warming to 1.5–2°C

12. Comparison Summary

Concept	Cause	Effect
Ozone Depletion	CFCs	UV increase
Greenhouse Effect	GHGs	Heat trapping
Global Warming	Enhanced greenhouse effect	Temperature rise

13. Memory Tricks

CFC → Cl → Ozone destruction
CO₂ → IR absorption → Warming
Global warming → Glacier melting → Sea level rise

14. Model Answer (10 Marks)

Global warming is the increase in Earth’s average temperature due to enhanced greenhouse effect. It is caused by greenhouse gases such as CO₂, CH₄, and N₂O. Major sources include fossil fuel combustion, deforestation, and agriculture. Effects include sea level rise, climate change, and biodiversity loss. It can be controlled by renewable energy, afforestation, and international agreements like the Paris Agreement.

Conclusion

Environmental pollution, particularly ozone depletion, greenhouse effect, and global warming, represents a major global challenge. Scientific understanding and international cooperation are essential for sustainable development and environmental protection.

Environmental Chemistry: RPSC 1st Grade Scientific Question Bank

1. In the stratosphere, the formation of Ozone (O3) from Oxygen (O2) is initiated by UV radiation of wavelength:
(A) > 400 nm
(B) < 242 nm
(C) 300-400 nm
(D) > 700 nm

Answer: (B) < 242 nm (Short wavelength UV-C dissociates O2 into oxygen atoms)

2. Which of the following acts as a "Chlorine Sink" in the stratosphere, preventing further ozone depletion?
(A) CCl2F2
(B) CH4 and NO2
(C) O3
(D) UV-B rays

Answer: (B) CH4 and NO2 (They react with Cl and ClO to form HCl and ClONO2, respectively)

3. The 'Ozone Hole' is most prominent over Antarctica during which month?
(A) January-February
(B) May-June
(C) September-October
(D) December

Answer: (C) September-October (During the Southern Hemisphere spring)

4. Which CFC is commonly known as Freon-12?
(A) CFCl3
(B) CF2Cl2
(C) CF3Cl
(D) C2F4Cl2

Answer: (B) CF2Cl2

5. The catalytic efficiency of CFCs in ozone depletion is high because:
(A) They are highly reactive in troposphere
(B) Chlorine atoms are regenerated in a chain reaction
(C) They absorb IR radiation
(D) They are water soluble

Answer: (B) Chlorine atoms are regenerated in a chain reaction

6. What is the mixing ratio of Ozone in the troposphere that is considered "harmful"?
(A) > 0.1 ppm
(B) < 0.01 ppm
(C) 10 ppm
(D) 100 ppm

Answer: (A) > 0.1 ppm

7. The Dobson Unit (DU) measures the total column of ozone. 100 DU corresponds to a thickness of:
(A) 1 cm
(B) 1 mm
(C) 0.1 mm
(D) 10 mm

Answer: (B) 1 mm (At STP)

8. Which radical is primarily responsible for the natural (non-anthropogenic) depletion of ozone?
(A) Cl•
(B) OH•
(C) NO•
(D) Both B and C

Answer: (D) Both B and C (Hydroxyl and Nitric Oxide radicals)

9. UV-B radiation (280-320 nm) exposure in humans primarily causes:
(A) Lung Cancer
(B) Cataracts and Skin Cancer
(C) Typhoid
(D) Night Blindness

Answer: (B) Cataracts and Skin Cancer

10. Polar Stratospheric Clouds (PSCs) are also known as:
(A) Noctilucent clouds
(B) Nacreous clouds
(C) Cumulus clouds
(D) Cirrus clouds

Answer: (B) Nacreous clouds (Type II)

11. Greenhouse gases absorb radiation in which region of the spectrum?
(A) Ultraviolet
(B) Visible
(C) Infrared
(D) X-ray

Answer: (C) Infrared (Specifically long-wave Earth radiation)

12. Which of the following has the highest Global Warming Potential (GWP) over a 100-year period?
(A) CO2
(B) CH4
(C) N2O
(D) SF6

Answer: (D) SF6 (Sulfur Hexafluoride ~23,900 times more potent than CO2)

13. The percentage contribution of Methane (CH4) to global warming is approximately:
(A) 60%
(B) 20%
(C) 14%
(D) 6%

Answer: (B) 20% (CO2 is 60%, CFCs 14%, N2O 6%)

14. Why is Nitrogen (N2) NOT a greenhouse gas?
(A) It is too heavy
(B) It does not have a dipole moment change during vibration
(C) It absorbs UV
(D) It is present in 78%

Answer: (B) It does not have a dipole moment change during vibration (Homonuclear diatomic)

15. 'Global Dimming' is caused by:
(A) Greenhouse gases
(B) Aerosols and Particulates
(C) Ozone depletion
(D) Deforestation

Answer: (B) Aerosols and Particulates (They reflect sunlight into space)

16. The "Atmospheric Window" through which Earth's radiation escapes to space lies between:
(A) 2-5 μm
(B) 8-13 μm
(C) 15-20 μm
(D) 25-30 μm

Answer: (B) 8-13 μm

17. Which protocol is specifically aimed at reducing Greenhouse Gas emissions?
(A) Montreal Protocol
(B) Kyoto Protocol
(C) Basel Convention
(D) Ramsar Convention

Answer: (B) Kyoto Protocol

18. Ocean acidification is a direct consequence of the increase in:
(A) O2
(B) N2
(C) CO2
(D) Ar

Answer: (C) CO2 (Formation of Carbonic acid H2CO3)

19. The "Albedo" of Earth refers to:
(A) Heat absorbed
(B) Sunlight reflected
(C) CO2 concentration
(D) Temperature of core

Answer: (B) Sunlight reflected back to space

20. Which GHG is produced primarily through the use of nitrogenous fertilizers?
(A) N2
(B) NO2
(C) N2O
(D) NH3

Answer: (C) N2O (Nitrous Oxide)

21. Biochemical Oxygen Demand (BOD) for "Clean Water" should be:
(A) < 5 ppm
(B) > 17 ppm
(C) 50 ppm
(D) 100 ppm

Answer: (A) < 5 ppm (Highly polluted water is > 17 ppm)

22. Which reagent is used in the determination of Chemical Oxygen Demand (COD)?
(A) K2Cr2O7 in acidic medium
(B) KMnO4 in basic medium
(C) Na2S2O3
(D) Phenolphthalein

Answer: (A) Potassium dichromate in acidic medium

23. Excess Fluoride (> 10 ppm) in drinking water leads to:
(A) Blue Baby Syndrome
(B) Methemoglobinemia
(C) Skeletal Fluorosis
(D) Kidney stones

Answer: (C) Skeletal Fluorosis (Mottling of teeth occurs at 2 ppm)

24. Which metal ion contamination caused the "Itai-Itai" disease in Japan?
(A) Hg2+
(B) Cd2+
(C) Pb2+
(D) As3+

Answer: (B) Cadmium (Cd2+)

25. Acid rain is defined as rain with a pH below:
(A) 7.0
(B) 6.5
(C) 5.6
(D) 4.0

Answer: (C) 5.6 (Normal rain is 5.6 due to CO2)

26. In Photochemical Smog, the primary precursor is:
(A) SO2
(B) Nitrogen Oxides and Hydrocarbons
(C) CO2
(D) Smoke

Answer: (B) Nitrogen Oxides (NOx) and volatile organic compounds

27. The catalyst used in the production of H2SO4 in the atmosphere during acid rain is:
(A) V2O5
(B) Particulate matter/Aerosols
(C) Fe
(D) Pt

Answer: (B) Particulate matter (and soot particles)

28. Which of the following is a "Secondary Pollutant"?
(A) CO
(B) NO
(C) PAN (Peroxyacetyl nitrate)
(D) SO2

Answer: (C) PAN

29. The maximum prescribed limit of Nitrate in drinking water is:
(A) 50 ppm
(B) 10 ppm
(C) 100 ppm
(D) 1 ppm

Answer: (A) 50 ppm

30. Which organic compound is used as a 'Blowing Agent' in the manufacture of polystyrene?
(A) CFCs
(B) CO2
(C) CH4
(D) Argon

Answer: (A) CFCs (Modern alternatives use CO2 or Pentane)

31. The solubility of Oxygen in water _______ with an increase in temperature.
(A) Increases
(B) Decreases
(C) Remains same
(D) First increases then decreases

Answer: (B) Decreases

32. Which gas is a major "Sink" for the Hydroxyl (OH) radical?
(A) CO2
(B) CH4
(C) N2
(D) Ar

Answer: (B) CH4 (Methane)

33. The 'Stone Leprosy' of Taj Mahal is caused by:
(A) Fungi
(B) Acid Rain
(C) Heat
(D) De-icing salts

Answer: (B) Acid Rain (H2SO4 converts CaCO3 to CaSO4)

34. "Eutrophication" of water bodies is primarily caused by:
(A) Heavy metals
(B) Phosphates and Nitrates
(C) Detergents only
(D) Thermal pollution

Answer: (B) Phosphates and Nitrates (from fertilizers and sewage)

35. Classical Smog is chemically:
(A) Oxidizing
(B) Reducing
(C) Neutral
(D) Amphoteric

Answer: (B) Reducing (Contains SO2 and smoke)

36. The pollutant 'Black Carbon' affects climate by:
(A) Absorbing solar energy
(B) Increasing albedo
(C) Decomposing CO2
(D) Cooling the Earth

Answer: (A) Absorbing solar energy

37. Which compound is used in "Green Chemistry" as a safer solvent for dry cleaning?
(A) Tetrachloroethene
(B) Liquefied CO2
(C) H2O2
(D) Benzene

Answer: (B) Liquefied CO2

38. The pH of the 'Ocean Surface' is approximately:
(A) 5.1
(B) 7.0
(C) 8.1
(D) 10.5

Answer: (C) 8.1 (Slightly alkaline)

39. Which gas was found in high concentration in the troposphere over the "Asian Brown Cloud"?
(A) Ozone
(B) Black Carbon and Fly Ash
(C) CFCs
(D) Neon

Answer: (B) Black Carbon and Fly Ash

40. Which pollutant causes the leaf curling in plants?
(A) SO2
(B) CO
(C) Fluoride
(D) PAN

Answer: (A) SO2 (Causes necrosis and chlorosis)

41. In the Chapman Cycle, the "odd oxygen" species are:
(A) O2 and O3
(B) O and O3
(C) O and O2
(D) O, O2, and O3

Answer: (B) O and O3

42. Which species is a temporary 'Reservoir' for bromine in the stratosphere?
(A) Br2
(B) HBr
(C) BrONO2
(D) Both B and C

Answer: (D) Both B and C

43. The residence time of CO2 in the atmosphere is roughly:
(A) 5 days
(B) 100-200 years
(C) 1000 years
(D) 1 month

Answer: (B) 100-200 years

44. Which process removes NOx from the stratosphere naturally?
(A) Precipitation
(B) Conversion to HNO3 and subsequent washout
(C) UV photolysis
(D) Reaction with CO

Answer: (B) Conversion to HNO3 and subsequent washout

45. The "Synergistic Effect" in air pollution refers to:
(A) One pollutant neutralizing another
(B) Combined effect being greater than the sum of individual effects
(C) Dilution of gases
(D) Only primary pollutants acting

Answer: (B) Combined effect being greater than the sum of individual effects

46. Which of the following is a sink for Nitrogen Oxides?
(A) Ocean water
(B) Soil
(C) Both A and B
(D) None

Answer: (C) Both A and B

47. Peroxyacetyl nitrate (PAN) is formed by the reaction of:
(A) Hydrocarbons + NO2 + O3
(B) CO + NO2
(C) SO2 + O2
(D) CO2 + H2O

Answer: (A) Hydrocarbons + NO2 + O3

48. Lead pollution from automobiles has been reduced by using:
(A) Unleaded petrol
(B) Leaded petrol
(C) High sulfur diesel
(D) Alcohol

Answer: (A) Unleaded petrol (MTBE is often used as a substitute)

49. High concentrations of CO (Carbon Monoxide) lead to:
(A) Hypoxia
(B) Hyperoxia
(C) Leukemia
(D) Bone marrow failure

Answer: (A) Hypoxia (Due to Carboxyhaemoglobin formation)

50. "Green Chemistry" is also known as:
(A) Environmental Chemistry
(B) Sustainable Chemistry
(C) Bio-chemistry
(D) Soil Chemistry

Answer: (B) Sustainable Chemistry

Note: These questions are strictly based on NCERT Chemistry (Class 11 & 12) and standard atmospheric chemistry reference books. Ideal for RPSC 1st Grade and GATE Chemistry candidates.