Ozone Layer Depletion - UNSOLVED PRACTICE SET

Q7. Write the reactions showing the formation of ozone in the stratosphere. Why is this process called the Chapman cycle?

Q8. Explain the mechanism of ozone depletion by CFCs. Why is chlorine called a catalyst in this process?

Q9. Why is the ozone hole more prominent over Antarctica than over the Arctic?

Q10. What are the health consequences of increased UV-B radiation reaching the Earth's surface due to ozone depletion?

Q11. Your refrigerator at home uses R-134a instead of older CFCs. Explain why this change was made and whether R-134a is completely harmless.

Q12. Why did the Montreal Protocol succeed where other environmental agreements have struggled? What role did India play in this protocol?

Q13. Discuss ozone layer depletion in detail:

(a) The formation of ozone in the stratosphere — Chapman cycle reactions

(b) Natural processes that maintain ozone balance

(c) Mechanism of ozone depletion by CFCs and halons — initiation, propagation, and termination steps

(d) Why polar stratospheric clouds (PSCs) accelerate ozone depletion over Antarctica

(e) The discovery of the ozone hole by the British Antarctic Survey in 1985

Q14. Explain the international response to ozone depletion and current status:

(a) The Vienna Convention (1985) and Montreal Protocol (1987) — key provisions

(b) Amendments to the protocol: London (1990), Copenhagen (1992), Beijing (1999)

(c) India's role — phase-out schedule for CFCs, halons, and HCFCs

(d) Current status — is the ozone layer recovering? Latest scientific assessments

(e) The Kigali Amendment (2016) — addressing HFCs as greenhouse gases

Q15. Ozone depletion has direct relevance to India's population and economy. Discuss:

(a) Why Indians with darker skin have some natural protection against UV-B, but are still at risk for cataracts and immune suppression

(b) The impact of increased UV-B on Indian agriculture — reduced yields of wheat, rice, and soybeans

(c) Why the phase-out of CFCs in India's refrigeration and air conditioning sector was challenging but successful

(d) The emergence of "ozone-friendly" technologies in India and their economic implications

Q16. The total ozone column over Antarctica in October 1980 was 300 Dobson Units (DU). In October 2000, it dropped to 100 DU.

(a) Calculate the percentage depletion of ozone.

(b) If the ozone layer is recovering at 1% per year since 2000, calculate when it will return to 250 DU.

(c) The area of the ozone hole in 2006 was 29.6 million km². If it has decreased by 20% since then, calculate the current area.

Q17. A single CFC molecule (CFCl₃) in the stratosphere releases one chlorine atom, which can catalytically destroy ozone.

(a) Write the catalytic cycle showing chlorine destroying ozone.

(b) If one chlorine atom destroys 100,000 ozone molecules before being removed, calculate the total ozone molecules destroyed by 1 kg of CFC-11 (CFCl₃).

(c) If the molar mass of CFC-11 is 137.5 g/mol, calculate the number of CFC-11 molecules in 1 kg.

[Given: Avogadro's number = 6.022 × 10²³]

Q18. India phased out 10,000 tonnes of CFC production by 2010 as per the Montreal Protocol.

(a) If the cost of replacing CFC technology with HFC technology was ₹ 500 crore, calculate the cost per tonne of CFC phased out.

(b) The Multilateral Fund provided ₹ 300 crore for this transition. Calculate the percentage of costs covered by international funding.

(c) If each tonne of CFC had a global warming potential equivalent to 4,000 tonnes of CO₂, calculate the total CO₂-equivalent emissions avoided by this phase-out.