Environmental chemistry
This article explores the dependence of O2 and O3 dissociation on light wavelength, detailing the photodissociation processes. It explains the catalysis mechanisms of ozone depletion by chlorofluorocarbons (CFCs) and nitrogen oxides (NOx), including the significant reactions involved. Additionally, it outlines why ozone depletion occurs more prominently in polar regions, attributed to very cold winter temperatures, ice crystal formation, and subsequent UV light interactions that release chlorine radicals. This analysis highlights the complex interplay of chemical reactions leading to ozone layer deterioration.
Environmental chemistry
E N D
Presentation Transcript
Environmental chemistry E. 9 ozone
ozone Explain the dependence of O2 and O3 dissociation on the wavelength of light. Describe the mechanism in the catalysis of O3 depletion by CFCs and NOx. Outline the reasons for greater ozone depletion in polar regions.
photodissociation photodissociation of O2 photodissociation of O3
Catalytic depletion by NO2 • NO2 NO + O2 • NO + O3 NO2 + O2 • NO2 + O NO + O2 • Net: O + O3 2O2
greater ozone depletion in polar regions very cold winter temperatures over the polar regions ice crystals form in the stratosphere and act as heterogeneous catalysts for reactions which produce chlorine oxides (e.g. HOCl) and Cl2 from CFCs. during winter time a huge reservoir of HOCl and Cl2 molecules builds up until spring arrives. spring brings UV light which causes chlorine free radicals to split from the HOCl or Cl2 molecules. greater catalytic depletion of the ozone in the polar regions. UV also melts the ice crystals and stops the formation of HOCl and Cl2 slowing down this process.
