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Understanding Stratospheric Chemistry: Ozone Depletion and Catalyst Families

This quiz explores the intricate aspects of stratospheric chemistry, focusing on ozone depletion mechanisms driven by various catalytic families. Key topics include HOx, NOx, ClOx, and BrOx species, their sources, sinks, and reservoirs in the atmosphere. Students will learn about the resilience of catalysts to tropospheric loss processes and the impact of trace species on ozone depletion. Additionally, the quiz prompts a real-world question on modifying CFC structures to mitigate their contribution to stratospheric chlorine while retaining necessary physical properties.

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Understanding Stratospheric Chemistry: Ozone Depletion and Catalyst Families

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  1. CHEM 304 - 2/17/12 I.B. Stratospheric chemistry: Ozone Catalytic Ozone Depletion - Catalyst “Families” (HOx, NOx, ClOx) - Reservoirs and Sinks QUIZ #2: M

  2. 3 Main (1 + additional) Catalytic Families: “HOx”: H, OH, HO2 “NOx”: NO, NO2, (NO3- technically not included) “ClOx”: Cl, ClO, (ClO2) “BrOx”: Br, BrO, (BrO2- ? May not exist ?)

  3. Some lingo regarding “Trace species” (e.g. pollutants, reactive substances, etc.) Source: reaction or process that release trace compound. Sink: Reaction or process that “permanently” removes trace compound. Reservoir: An entity (process, substance, physical feature) that temporarily holds a trace substance

  4. Catalyst Sources: Substance must be resilient to these key (tropospheric) loss processes. • Wet Deposition or “rain out”: Is it H2O Soluble? • Reaction w/ OH: Does it have an H? • Photochemistry: Does it absorb >300nm?

  5. Vertical Distribution of CFC’s…

  6. A real world question: How might you modify the structure of a CFC to yet reduce its contribution to stratospheric ClOx, yet retain, as much as possible, its physical properties? (Hint: How would you keep it out of the stratosphere …)

  7. Contributions to stratospheric Chlorine “load” – this graphic does not work

  8. UV/VIS Spectrum of HO-NO2 (i.e. HNO3)  = 1.2 x106 sec. = ~ 14 days

  9. UV/VIS Spectrum of ClO-NO2  = 1.7 x104 sec. = ~ 4.7 hours

  10. UV/VIS Spectrum of BrO-NO2  = 2 x103 sec. = ~ 0.55 hours!

  11. UV/VIS Spectrum of HO-NO2 (i.e. HNO3)  = 1.2 x106 sec. = ~ 14 days (altitude average … shorter in stratosphere)

  12. UV/VIS Spectrum of ClO-NO2  = 1.7 x104 sec. = ~ 4.7 hours

  13. UV/VIS Spectrum of BrO-NO2  = 2 x103 sec. = ~ 0.55 hours!

  14. Why BrOx is so much more destructive than ClOx: UV Spectra of HCl and HBr

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