Photo AI
The images below represent the concentration of ozone in the atmosphere above Antarctica near the South Pole for the years 1979, 1994, and 2012, measured at the same time each year - HSC - SSCE Chemistry - Question 30 - 2013 - Paper 1
Question 30
The images below represent the concentration of ozone in the atmosphere above Antarctica near the South Pole for the years 1979, 1994, and 2012, measured at the same... show full transcript
Worked Solution & Example Answer:The images below represent the concentration of ozone in the atmosphere above Antarctica near the South Pole for the years 1979, 1994, and 2012, measured at the same time each year - HSC - SSCE Chemistry - Question 30 - 2013 - Paper 1
Step 1
Identify the changes in ozone concentration between 1979 and 1994
Answer
Between 1979 and 1994, there was a significant decrease in ozone concentration above the South Pole. This decrease can be attributed to the release of chlorine from chlorofluorocarbons (CFCs), which are substances known to deplete ozone in the stratosphere.
Step 2
Discuss the role of CFCs and relevant equations
Answer
The mechanism of ozone depletion involves the dissociation of CFCs when exposed to UV light, releasing chlorine atoms that catalytically destroy ozone. The reactions can be represented as follows:
ightarrow ext{CCl}_2 ext{F} + ext{Cl} \ \ ext{Cl} + ext{O}_3 ightarrow ext{ClO} + ext{O}_2 $$ Each chlorine atom can destroy thousands of ozone molecules before it is removed from the stratosphere.Step 3
Identify the changes in ozone concentration from 1994 to 2012
Answer
From 1994 to 2012, the concentration of ozone began to increase. This change is largely due to international agreements like the Montreal Protocol, which aimed to phase out the use of ozone-depleting substances. The decrease in CFC emissions has allowed for a gradual recovery of the ozone layer.
Step 4
Provide relevant equations for ozone concentration recovery
Answer
The recovery of the ozone layer, while gradual, can be modeled but is subject to various atmospheric variables. The general understanding is that reduced chlorine levels lead to a restoration of balance in ozone formation, represented by:
ightarrow 2 ext{O} \ \ ext{O} + ext{O}_2 ightarrow ext{O}_3 $$ This illustrates the natural formation of ozone in the stratosphere.