5.4-5.5: UV-radiation damage

Question 1

the conversion of O3 –> O2 is…

Answer 1

exothermic (releases energy)

Question 2

the conversion of O2 –> O3 is…

Answer 2

endothermic (requires energy)

Question 3

where does the energy come from to convert O2 –> O3?

Answer 3

UV photons

Question 4

the UV shield is created by

Answer 4

UV photons

Question 5

Steady-state concentration

Answer 5

total formation rate = total destruction rate

Question 6

4 catalyst molecules that destruct stratospheric O3

Answer 6

HO⦁, Cl, Br, NOx

Question 7

HO⦁ are responsible for ___ of O3 destruction in lower stratosphere

Answer 7

½

Question 8

how do increased CH4 emissions contribute to O3 formation?

Answer 8

↑ CH4 emissions = ↑ warming = ↑ rate of water evaporation = ↑ product of HO⦁
- HO⦁ = catalyst for destruction reaction

Question 9

what are halons used for?

Answer 9

fire extinguishers
- Non-toxic, non-flammable = not subject to oxidation

Question 10

how to halons destroy ozone?

Answer 10

Low reactivity in troposphere = only destroyed in stratosphere by UV photons

Question 11

where/how are NO⦁ produced?

Answer 11

produced in lower atmosphere by combustion/lightening

Question 12

how is NOx involved in destruction of ozone?

Answer 12

• Reaches stratosphere = photolyzed by UV –> N2 + O*
• Provides catalytic chain mechanisms for O3 destruction AND inhibits major mechanisms of O3 destruction

Question 13

Tropospheric source molecules

Answer 13

• activated by O* or UV  destroying O3 free radical chain carriers
• H2O, N2O, CFCs, Halons