ozone depletion

Question 1

what is the importance of stratospheric ozone

Answer 1

• important in the prevention of high-energy UV solar radiation from reaching the Earths surface causing biological damage

Question 2

what are the effects of UV on living organisms

Answer 2

• breaks up biological molecules causing
• skin damage
• skin cancer
• cataracts
• leaf tissue damage
• reduced photosynthesis

Question 3

what are CFCs and why were they used

Answer 3

• a chemical developed for use in air conditioning, refrigerators, and aerosol propellants
• boiling points close enough to ambient temps so gases can be liquified easily
• ability to dissolve grease and oils but not damage electrical components
• not flammable
• non-toxic

Question 4

outline the Rowland-Molina hypothesis

Answer 4

• the suggestion that the chemical properties of CFCs could lead to stratospheric ozone depletion due to
  1) the chemical stability of CFCs allowing them to remain in the atmosphere
  2) the dissociation by UV and release of chlorine radicals
  3) the reaction of chlorine with oxygen

Question 5

outline natural ozone formation

Answer 5

1) UV splits O2 into 2 monoatomic oxygens

2) monatomic oxygen reacts with an O2 molecules to form a triatomic ozone molecule

Question 6

outline natural ozone destruction

Answer 6

1) UV splits an O3 molecule into a stable O2 and a reactive monatomic oxygen

Question 7

outline how CFCs disrupt the dynamic equilibrium between ozone formation and destruction

Answer 7

1) CFCs are split by UV producing chlorine radical
2) this radical reacts with monatomic oxygen preventing the formation with O2 to form ozone
3) therefore more ozone is destroyed than made

Question 8

why is ozone depletion of Antarctica worse

Answer 8

1) stratospheric temps in Antarctica are much lower allowing the formation of stratospheric clouds and ice crystals
2) ice crystals provide surfaces for chemical reactions to take place producing chlorine molecules from CFCs
3) winds around create a polar vortex which maintains low temps and produces higher conc of chlorine as it’s not distributed

Question 9

outline the Montreal protocol

Answer 9

an international agreement which aimed to 
1 )ban the manufacture and use of CFCS
2 )use of alternative processes
3) use of alternative material s
4) disposal of existing CFCS

Question 10

list some alternative processes to CFC

Answer 10

1) pump actions sprays

2) stick or roll-on deodrants

Question 11

list some alternative materials to CFCs

Answer 11

1) HCFCs as they are less chemically stable so don’t reach the stratosphere
2) CFCs in foam plastics replaced with HCFCs and HFCs
3) CFCs in asthma inhalers replaced with HFSa

Question 12

outline the safe disposal of CFCs

Answer 12

• existing CFCs are incinerated and broken down into carbon dioxide and acidic gases that can be neutralized with crushed lime