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cycle 1: Cl + O 3 → ClO + O 2 ClO + O → Cl + O 2 Net : O 3 + O → 2O 2 tropical and middle latitudes requires UV radiation to form atmic oxygen. cycle 2: ClO + ClO → (ClO) 2 (ClO) 2 + sunlight → ClOO + Cl ClOO → Cl + O 2 2 (Cl + O 3 → ClO + O 2 )
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cycle 1: • Cl+ O3 → ClO + O2 • ClO + O → Cl + O2 • Net: O3+ O → 2O2 • tropicalandmiddlelatitudes • requires UV radiationto form atmicoxygen cycle 2: ClO + ClO → (ClO)2 (ClO)2 + sunlight → ClOO + Cl ClOO → Cl + O2 2 (Cl + O3 → ClO + O2) Net: 2O3 → 3O2 cycle 3: ClO + BrO → Cl + Br + O2 or (ClO + BrO → BrCl + O2 BrCl + sunlight → Cl + Br) Cl + O3 → ClO + O2 Br + O3 → BrO + O2 Net: 2O3 → 3O2 Q9: What are the chlorine and bromine reactions that destroy stratospheric ozone? • cycle 2 + 3 • polar region • visiblesunlightrequiredtocompleteeachcycle, helpsto form ClO • latewinter/early spring – ozonedestruction > ozoneproduction
Uncertainties/Problems: • chlorine and bromineareonly one group of ozone destroying substances • other groups e.g. reactive hydrogen, reactive nitrogen gas • increase/decrease of substances in the future • might be difficult to estimate consequences of an increase of a substance