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Chapter 2 (CIC) and Chapter 18 (CTCS)

Chapter 2 (CIC) and Chapter 18 (CTCS). Read in CTCS Chapter 18.1-3 Problems in CTCS: 1, 7, 9, 11, 13. The Ozone Hole. Ozone varies with the seasons Sun’s star spot cycles 11-12 years Winds that are seasonal and 28 month cycles. Average [O 3 ] over Northern US = 320 DU Equator = 250 DU

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Chapter 2 (CIC) and Chapter 18 (CTCS)

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  1. Chapter 2 (CIC) and Chapter 18 (CTCS) • Read in CTCS Chapter 18.1-3 • Problems in CTCS: 1, 7, 9, 11, 13

  2. The Ozone Hole • Ozone varies with the seasons • Sun’s star spot cycles 11-12 years • Winds that are seasonal and 28 month cycles Average [O3] over Northern US = 320 DU Equator = 250 DU Antarctica (’57) = 320 DU Antarctica (’97) = 120 DU

  3. Why is it Disappearing? • Generation of radicals destroys ozone • H2O + h  H. + .OH • NO. • CCl2F2 + h  Cl. + .CClF2   220 nm O3 + 2 Cl.2 ClO. + O2 2 ClO. Cl2O2 Cl2O2 + UV photon  .ClO2 + Cl. .ClO2 + UV photon  Cl.+ O2 2 O3  3 O2 with Cl.as a catalyst (105 turnovers)

  4. Why Use CFC’s? • Correct b.p. • Not flammable • Not poisonous • Cheap • Inert • Allows them to make their way into the stratosphere where UV light can attack them (average lifespan is 120 years)

  5. What Evidence is There That CFC’s are Guilty?“Smoking Gun” *Stanitski, D.L.; Eubanks, L.P.; Middlecamp, C.H.; Stratton, W.J. Chemistry in Context: Applying Chemistry to Society, 3rd Edition, McGraw-Hill, Boston, MA, 2000, pg 78.

  6. Why over Antarctica and Not the North Pole? • Coldest spot at -90ºC • Water freezes into frozen clouds providing a surface • We’re seeing decreases in the north, but it is not classified as a “hole” • Winds in the north are much more significant

  7. What’s Being Done About it? • Montreal Protocol 1987 • Reduce CFC’s to ½ 1986 levels by 1998 • London 1990 • Ban CFC’s by 2000 (done by 1996) • Copenhagen 1992 • Use HCFC’s but must stop these by 2030 • HCFC’s are 5% as efficient as CFC’s at destroing ozone • Montreal 1997 • Elimination of CCl4, CH3Br between 2000 and 2005

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