上海交通大学：《大学化学》教学资源_加州理工课件学习_Series07AtmosphericChemistry

Clouds are the Earth's Blanket VII-1

Clouds are the Earth’s Blanket VII-1

The Chemistry of Stratospheric Ozone Depletion Chemistry and Photochemistry in the Stratosphere The Antarctic Ozone Hole Molecular Beam/Laser Spectroscopic Studies of Photochemistry VII-2

The Chemistry of Stratospheric Ozone Depletion • Chemistry and Photochemistry in the Stratosphere • The Antarctic Ozone Hole • Molecular Beam/Laser Spectroscopic Studies of Photochemistry VII-2

Ozone in the News DEB知strs R for Health Care Nations meet in Montreal to discuss global TIME agreement on banning CFC chemicals,not usually done except for chemical warfare ageints. CFC's are in everyone's home already,so they're not killing anyone right now. Rush Limbaugh says it's a fraud,a scientific consipracy,grant grubbing,and government just interfering with our lives. THE DANGER MOVES CLOSER TO HOME →What's going on? An otherwise arcane area of chemistry catapulted into international prominence.A combination of lab measurements,satellite data,plane flights,and physical chemistry is needed to piece the puzzle together of why ozone is being lost. VII-3

➩ Nations meet in Montreal to discuss global agreement on banning CFC chemicals, not usually done except for chemical warfare ageints. ➩ CFC's are in everyone's home already, so they're not killing anyone right now. ➩ Rush Limbaugh says it's a fraud, a scientific consipracy, grant grubbing, and government just interfering with our lives. ➩ What's going on? ➩ An otherwise arcane area of chemistry catapulted into international prominence. A combination of lab measurements, satellite data, plane flights, and physical chemistry is needed to piece the puzzle together of why ozone is being lost. Ozone in the News VII-3

A Problem with No National Boundaries Air Conditioner Repair Man Arizona says CFC's are OK CFC's smuggled in from Mexico,which also OK's CFC's VII-4

A Problem with No National Boundaries Air Conditioner Repair Man Arizona says CFC’s are OK CFC’s smuggled in from Mexico, which also OK’s CFC’s VII-4

The Ozone Shield Our Ozone Shield Less than 0.5%of Earth's Radius: Protects all life on earth VII-5

The Ozone Shield Less than 0.5% of Earth’s Radius; Protects all life on earth VII-5

Temperature Profile in the Atmosphere Thermosphere 100 Mesopause 80 Mesosphere 60 Stratopause-------- Stratosphere 40 Stratosphere T increases with increasing altitude; Due to absorption of sunlight by ozone From 15-60 km 20 Tropopause Troposphere Troposphere T decreases with increasing altitude; 150 200 250 300 Adiabatic cooling as density gets lower T(K) Minimum defines tropopause VII-6

Temperature Profile in the Atmosphere Troposphere T decreases with increasing altitude; Adiabatic cooling as density gets lower Minimum defines tropopause Stratosphere T increases with increasing altitude; Due to absorption of sunlight by ozone From 15-60 km VII-6

Molecular Oxygen O2,Dioxygen Octet on each atom Stable 0-0 r=1.208A BDE 117.1 kcal/mol 21%of atmosphere Ozone Ozone,03 Non-octet .0-0-c r=1.278A 4 times weaker bond a=116.8deg Reactive and caustic BDE 24.0 kcal/mol VII-7

O2 , Dioxygen Octet on each atom Stable Ozone, O3 Non-octet O=O O-O=O 21% of atmosphere 4 times weaker bond Reactive and caustic . . • • • • • • • • • • • • • • • • • • VII-7

Ozone Absorption Spectrum OZONE 200 220 240 260 280 300 WAVELENGTH(nm) Absorbs light between 220 and 300 nm N2 and O2 do not absorb at those wavelengths Protects DNA from UV light and damage VII-8

Ozone Absorption Spectrum Absorbs light between 220 and 300 nm N2 and O2 do not absorb at those wavelengths Protects DNA from UV light and damage VII-8

Chapman Cycle:1930's Ozone Destruction Light absorption breaks the O-O bond in ozone Forms O. Ozone Formation O In presence of a third P8→ body,forms O3 again 00 Does NOT explain ozone hole VII-9

Chapman Cycle: 1930’s Light absorption breaks the O-O bond in ozone Forms O In presence of a third body, forms O3 again Does NOT explain ozone hole Ozone Destruction Ozone Formation . VII-9

Concentration of Species in the Atmosphere 50 OXYGEN and HYDROGEN SPECIES (March 15-Local Noon-40 N) OH H*108 40 202 O(P) (u)opmnIy 30 03 HO2 O(D)*108 CH4 1018 20 10° 109 1010 1012 1014 Number Density (molecules/cm3) Water and Ozone are highest,by far Others are small,but they don't have 8 electrons! VI-10

Concentration of Species in the Atmosphere Water and Ozone are highest, by far Others are small, but they don’t have 8 electrons! VII-10