Answer: In recent years ozone in the stratosphere has been

Chapter 13, Problem 13.101

(choose chapter or problem)

In recent years ozone in the stratosphere has been depleted at an alarmingly fast rate by chlorofluorocarbons (CFCs). A CFC molecule such as CFCl3 is first decomposed by UV radiation: CFCl3 CFCl2 1 Cl The chlorine radical then reacts with ozone as follows: Cl 1 O3 ClO 1 O2 ClO 1 O Cl 1 O2 The O atom is from the photochemical decomposition of O2 molecules. (a) Write the overall reaction for the last two steps. (b) What are the roles of Cl and ClO? (c) Why is the fluorine radical not important in this mechanism? (d) One suggestion to reduce the concentration of chlorine radicals is to add hydrocarbons such as ethane (C2H6) to the stratosphere. How will this work? (e) Draw potential energy versus reaction progress diagrams for the uncatalyzed and catalyzed (by Cl) destruction of ozone: O3 1 O 2O2. Use the thermodynamic data in Appendix 3 to determine whether the reaction is exothermic or endothermic.