MCQs on Ozone Layer

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Ozone is an intriguing molecule with various implications, both beneficial and detrimental, across several domains. Here’s a comprehensive note and MCQs covering its characteristics, formation, applications, and effects

MCQs on Ozone Layer practice now

Chemical Structure: Ozone (O3) is a molecule composed of three oxygen atoms. Its structure is different from the more common oxygen molecule (O2), where two oxygen atoms are bonded together.

Formation: Ozone can be generated naturally in the Earth’s atmosphere and artificially in laboratories. It is formed through various processes, primarily:

  • Stratospheric Formation: In the upper atmosphere, ozone is created when oxygen molecules (O2) are split by ultraviolet (UV) radiation from the sun, forming two oxygen atoms. These free oxygen atoms then combine with other oxygen molecules to form ozone.
  • Ground-Level Formation: Ozone can also be produced at ground level through chemical reactions involving pollutants from vehicle emissions, industrial activities, and other sources. Nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight to create ground-level ozone.

Properties of Ozone

  • Odor: Ozone has a distinct, sharp odor often detected after a thunderstorm or around electrical equipment.
  • Chemical Reactivity: It is a highly reactive molecule, capable of oxidizing a wide range of substances. This reactivity makes it both beneficial and potentially harmful.
  • Role in the Atmosphere: In the stratosphere, the ozone layer acts as a shield, absorbing a portion of the sun’s harmful UV radiation, protecting life on Earth from excessive exposure.

Applications of Ozone

1. Environmental Applications:

  • Water Treatment: Ozone is used to purify water by effectively killing bacteria, viruses, and other microorganisms. It’s an eco-friendly alternative to chlorine in water treatment plants.
  • Air Purification: Ozone generators are used to remove odors, kill airborne bacteria, and break down pollutants in the air.

2. Medical and Industrial Applications:

  • Medical Sterilization: Ozone’s disinfectant properties find use in medical settings for sterilizing equipment and purifying air and water.
  • Industrial Processes: Ozone is used in various industries for chemical synthesis, bleaching processes, and as an oxidizing agent.

Effects of Ozone

1. Environmental Impact:

  • Ozone Depletion: Human-made chemicals like chlorofluorocarbons (CFCs) have contributed to the depletion of the ozone layer, leading to the formation of the ozone hole, primarily over Antarctica. This depletion allows more harmful UV rays to reach the Earth’s surface, posing risks to ecosystems and human health.

2. Health Effects:

  • Respiratory Issues: High levels of ground-level ozone can cause respiratory problems, aggravate asthma, and lead to lung inflammation.
  • Eye Irritation: Ozone exposure can cause eye irritation and other eye-related issues.


Ozone, a molecule with a crucial role in the atmosphere’s protection and various applications in industries and healthcare, presents a delicate balance. While its presence in the stratosphere shields life from harmful UV radiation, its formation at ground level due to pollution poses environmental and health concerns. Understanding its properties and regulating its production is crucial to harness its benefits while mitigating its harmful effects on both the environment and human health.

MCQs on Ozone Layer

D) The ozone hole occurs primarily during winter months.

Q1. Place where Ozone Layer is primarily found is

(a) Troposphere 

(b) Stratosphere

(c) Mesosphere

(d) Ionosphere

(b) Stratosphere

Q2. Ozone layer is above the earth’s crust around

(a) 50 km.

(b) 300 km.

(c) 2000 km

(d) 20 km.

(d) 20 km

Q3. Which is the lowest layer of the Atmosphere?

(a) Stratosphere

(b) Ozonosphere

(c) Ionosphere 

(d) Troposphere

(d) Troposphere

Q4. Which is responsible for Ozone Hole?

(a) CO2 

(b) SO2  

(c) O2 

(d) CFC

(d) CFC

Q5. The radiation that is absorbed by ozone present in the  atmosphere is 

(a) Infrared 

(b) Visible  

(c) Ultraviolet 

(d) Microwave

(c) Ultraviolet

Q6. Ozone layer in atmosphere

(a) Produces rain

(b) Produces pollution  

(c) Provides safety to life on earth from ultraviolet  radiation

(d) Produces oxygen in the atmosphere

) Provides safety to life on earth from ultraviolet  radiation

Q7. Harmful ultraviolet radiation coming from the sun can  cause

(a) Liver cancer

(b) Brain cancer  

(c) Oral cancer  

(d) Skin cancer

(d) Skin cancer

Q8. The International Day for Preservation of Ozone layer  is observed on:

(a) 15th August 

(b) 16th September

(c) 24th October 

(d) 1st May

(b) 16th September

Q9. The ozone hole is caused by

(a) Acetylene 

(b) Ethylene

(c) Chlorofluorocarbons 

(d) Methane

(c) Chlorofluorocarbons

Q10. Formation of the ozone hole is maximum over 

(a) India 

(b) Africa  

(c) Antarctica 

(d) Europe

(c) Antarctica

Q11.Montreal Protocol is related to the protection of:

(a) Greenhouse gases

(b) Acid rain

(c) Ozone layer

(d) Endangered species

(c) Ozone layer

Q12. In stratosphere, the level of ozone is naturally regulated  by 

(a) Nitrous oxide

(b) Nitrogen dioxide  

(c) CFC 

(d) Water vapours

(b) Nitrogen dioxide

Q13. Which gas is filled in refrigerators?

(a) Ammonia 

(b) Mafron  

(c) Methane 

(d) Acetylene

(b) Mafron

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Q14. Which one of the following teams of scientists first  discovered the ‘ozone hole’ over Antarctica?

(a) Russian Team

(b) German Team

(c) American Team

(d) British Team

(d) British Team

Q15. Which layer of the Earth’s atmosphere contains the ozone layer?

A) Troposphere

B) Stratosphere

C) Mesosphere

D) Thermosphere

B) Stratosphere

Q16. What is the primary role of ozone in the atmosphere?

A) Absorbing ultraviolet (UV) radiation

B) Regulating Earth’s temperature

C) Producing oxygen

D) Facilitating cloud formation

A) Absorbing ultraviolet (UV) radiation

Q17. Which human activities contribute significantly to ozone depletion?

A) Burning fossil fuels

B) Using aerosol sprays containing chlorofluorocarbons (CFCs)

C) Industrial processes

D) All of the above

(d) All the above

Q18. What is the thinning of the ozone layer primarily caused by?

A) Nitrogen oxides

B) Sulfurdioxide

C) Carbon monoxide

D) Chlorine and bromine compounds

D) Chlorine and bromine compounds

Q19. What is the “ozone hole” primarily associated with?

A) Polar vortex

B) Ozone production

C) Ozone layer thinning

D) Stratospheric winds

C) Ozone layer thinning

Q20. Which of the following is a health effect of increased UV radiation due to ozone depletion?

A) Reduced risk of skin cancer

B) Weakened immune system

C) Improved vision

D) Stronger bones

B) Weakened immune system

Q21. Which natural factor can contribute to ozone depletion in specific circumstances?

A) Volcanic eruptions

B) Forest fires

C) Solar flares

D) None of the above

C) Solar flares

Q22. What measures can help prevent further ozone depletion?

A) Using ozone-friendly products

B) Implementing international agreements

C) Educating about ozone protection

D) All of the above

D) All of the above

Q23. Which specific chemical family was predominantly responsible for the depletion of the ozone layer?

A) Halons

B) Nitrous oxides

C) Halocarbons

D) Hydrocarbons

C) Halocarbons

Q24. What is the name of the process by which ozone molecules are broken down by chlorine atoms?

A) Ozone synthesis

B) Ozone depletion potential

C) Ozone destruction cycle

D) Ozone catalytic reaction

C) Ozone destruction cycle

Q25. What is the unit used to measure the ozone-depleting potential of substances?

A) Ozone Protection Units (OPU)

B) Ozone Depletion Units (ODU)

C) Ozone Depletion Potential (ODP)

D) Ozone Loss Metric (OLM)

C) Ozone Depletion Potential (ODP)

Q26. Which of the following statements about the ozone hole is true?

A) It forms due to the release of ozone-depleting substances in the stratosphere.

B) The ozone hole is a permanent opening in the ozone layer.

C) Its size and severity are consistent every year.

D) The ozone hole occurs primarily during winter months.

D) The ozone hole occurs primarily during winter months.

What is the ozone layer, and why is it important?

The ozone layer is a region of the Earth’s stratosphere that contains a higher concentration of ozone molecules. Its significance lies in its ability to absorb and block a portion of the sun’s harmful ultraviolet (UV) radiation, thus protecting life on Earth from excessive UV exposure. Without this layer, increased UV radiation could lead to higher rates of skin cancer, cataracts, and other health issues in humans, as well as harm to ecosystems and marine life.

How is the ozone layer being depleted?

Human-made chemicals known as chlorofluorocarbons (CFCs), found in refrigerants, aerosol propellants, and solvents, have been the primary cause of ozone depletion. When released into the atmosphere, these chemicals break down ozone molecules. Additionally, bromine-containing compounds found in some industrial processes and halons used in fire extinguishers contribute to ozone depletion.

Where is the ozone hole, and what are its implications?

The ozone hole refers to a severe depletion of ozone over Antarctica, particularly during the Southern Hemisphere’s spring. This phenomenon is linked to the use of CFCs and other ozone-depleting substances. The thinning of the ozone layer in this region allows increased levels of harmful UV radiation to reach the Earth’s surface, impacting ecosystems, marine life, and potentially increasing the risk of skin cancer and other health issues in humans.

What measures have been taken to address ozone depletion?

The Montreal Protocol, an international treaty adopted in 1987, aimed to phase out the production and use of ozone-depleting substances, such as CFCs and halons. This treaty has been successful in significantly reducing the production and consumption of these harmful chemicals, leading to gradual recovery of the ozone layer.

Is the ozone layer recovering, and what is the current status?

Studies indicate that the ozone layer is showing signs of recovery in response to the reduction in the use of ozone-depleting substances. However, complete recovery may take several decades. Scientists continue to monitor the ozone layer’s status, and while improvements are observed, ongoing vigilance and adherence to international agreements are crucial to sustaining and enhancing its recovery.

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