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Account for the changes in ozone concentration above Antarctica between 1979 and 2012 - HSC - SSCE Chemistry - Question 30 - 2013 - Paper 1
Question 30
Account for the changes in ozone concentration above Antarctica between 1979 and 2012. Your response should include relevant equations.
Worked Solution & Example Answer:Account for the changes in ozone concentration above Antarctica between 1979 and 2012 - HSC - SSCE Chemistry - Question 30 - 2013 - Paper 1
Step 1
Identify changes between 1979 and 1994
Answer
The concentration of ozone above the South Pole decreased between 1979 and 1994. The reduction in ozone levels can be attributed largely to the increase in chlorofluorocarbons (CFCs) in the atmosphere. These compounds are known to photodissociate, releasing chlorine radicals that catalyze the breakdown of ozone (O₃) into molecular oxygen (O₂).
Step 2
Step 3
Changes between 1994 and 2012
Answer
Since 1994, the atmospheric ozone concentration has begun to recover. This increase is attributed to international agreements such as the Vienna Convention and the Montreal Protocol, which mandated a reduction in the use of CFCs. The replacement of CFCs with substances that have a significantly lower ozone depletion potential (ODP) has facilitated the substantial recovery of the ozone layer.
Step 4
Conclusion and evidence from 2012 data
Answer
The 2012 data indicates an increase in ozone concentration above Antarctica compared to the levels observed in the previous years. The observed recovery trend in ozone levels is a positive sign of the effectiveness of international policy measures aimed at mitigating ozone depletion.