Write the essential function performed by ozone at the higher levels of the atmosphere. How is it formed in the upper atmosphere ? Write the name of the group of chemicals mainly responsible for the depletion of ozone layer.
Generated by claude-sonnet-4-6 · 2026-06-15 06:42 · grounding rag
Model Answer
Function of Ozone: Ozone (O₃) at the higher levels of the atmosphere shields the Earth's surface from harmful ultraviolet (UV) radiation from the Sun. UV radiation is highly damaging to organisms and can cause skin cancer in humans.
Formation: High-energy UV radiation splits molecular oxygen (O₂) into free oxygen atoms (O). These atoms then combine with O₂ to form ozone:
$$O_2 \xrightarrow{\text{UV}} O + O$$
$$O + O_2 \rightarrow O_3 \text{ (Ozone)}$$
Chemicals responsible: Chlorofluorocarbons (CFCs), used as refrigerants and in fire extinguishers, are mainly responsible for ozone layer depletion.
Source: Chapter 13, Section 13.2.1
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Explanation
- The question has three clear parts — examiners award 1 mark each: function, formation (with equations), and name of chemicals.
- Always write the chemical equations for ozone formation; they fetch marks.
- "CFCs" must be expanded as Chlorofluorocarbons — writing only the abbreviation may cost marks.
- Keep it concise; no extra detail needed beyond what is asked.