Lec-40-atmos - Chemical Reactions in the Atmosphere Photochemical reactions can generate free radicals Excitation h NO(g NO2(g 2 NO2(g NO(g O(g

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• Photochemical reactions can generate free radicals: Chemical Reactions in the Atmosphere h ν • Excitation: ·NO 2 (g) ·NO 2 * (g) •·NO 2 * (g) ·NO(g) + ·O·(g) h ν • Photodissociation: O 2 (g) ·O·(g) + ·O·(g) •Natural formation: •O 2 (g) ·O·(g) + ·O·(g) •·O·(g) + O 2 (g) O 3 (g) Ozone and Stratospheric Ozone Depletion h ν •Natural destruction: •O 3 (g) + ·O·(g) 2 O 2 (g) h ν UV protection: •O 3 (g) ·O·(g) + O 2 (g) •200 < λ < 310 nm absorbed. Stratospheric O 3 stops 95% to 99% of the sun’s UV radiation.
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The ozone “layer” is earth’s sunscreen -20 kilometers thick -At STP, would be a only few mm -Thinning of layer results in more UV penetration The ozone “layer” is earth’s sunscreen
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The ozone “layer” is earth’s sunscreen 20-90%
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• CFC-12: CF 2 C l 2 (g) CF 2 C l ·(g) + ·C l (g) Chlorofluorocarbons CFCs photodissociate: •·C l (g) + O 3 (g) C lO ·(g) + O 2 (g) •C lO ·+ C lO · C l OOC l l OOC l ·C l OO + ·C l l OO ·C l + O 2 (g) · C l
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This note was uploaded on 11/14/2010 for the course CHE 131 taught by Professor Kerber during the Spring '08 term at SUNY Stony Brook.

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Lec-40-atmos - Chemical Reactions in the Atmosphere Photochemical reactions can generate free radicals Excitation h NO(g NO2(g 2 NO2(g NO(g O(g

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