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Ozone Destruction by Atomic Chlorine

Advqm d Ixercise 6.9 Ozone Destruction by Atomic Chlorine... [Pg.271]

Advanced Exercise 7.2 Ozone Destruction by Atomic Chlorine Revisited... [Pg.282]

Compute the enthalpy change for the destruction of ozone by atomic chlorine by subtracting the dissociation energies of O2 and CIO from the dissociation energy for ozone. What model chemistry is required for accurate modeling of each phase of this process The experimental values are given below (in kcal-moT ) ... [Pg.137]

This technique cannot be applied to reactions which do not happen to be isodesmic (for example, destruction of ozone by atomic chlorine). [Pg.183]

Chlorine atoms are also very efficient ozone destruction catalysts, as noted originally by Stolarski and Cicerone (4) ... [Pg.26]

During the long Antarctic night, appreciable amounts of molecular chlorine, Cl, and hypochlorous acid, HOCl, accumulate within the polar vortex. When the sun returns during the spring (in September in Antarctica), ultraviolet radiation decomposes the accumulated molecular chlorine and hypochlorous acid to produce atomic chlorine. Cl. Atomic chlorine is a free radical. Free radicals are atoms or molecules that contain an unpaired or free electron. The Lewis structures of free radicals contain an odd number of electrons. The unpaired electron in free radicals makes them very reactive. The free radical Cl produced from the decomposition of CI2 and HOCl catalyzes the destruction of ozone as represented by the reaction ... [Pg.265]

Indeed, these reactions play an important role in the Antarctic ozone hole and they have important implications for control strategies, particularly of the bromi-nated compounds. For example, Danilin et al. (1996) examined the effects of ClO -BrO coupling on the cumulative loss of O-, in the Antarctic ozone hole from August 1 until the time of maximum ozone depletion. Increased bromine increased the rate of ozone loss under the denitrified conditions assumed in the calculations by converting CIO to Cl, primarily via reactions (31b) and (31c) (followed by photolysis of BrCl). Danilin et al. (1996) estimate that the efficiency of ozone destruction per bromine atom (a) is 33-55 times that per chlorine atom (the bromine enhancement factor ) under these conditions in the center of the Antarctic polar vortex, a 60 calculated as a global average over all latitudes, seasons, and altitudes (WMO, 1999). [Pg.705]

Estimates are that CFCs are so stable that they remain in the atmosphere from 80 to 120 years, and they are now spread throughout the atmosphere. Even in the most remote location, there are no fewer than 25 trillion CFC molecules in every liter of air you breathe Molina. Rowland, and Crutzen realized that CFC molecules reaching the stratosphere are Iragmented when exposed to the harsh ultraviolet rays at this altitude, as illustrated in Figure 17.18. One of these fragments is atomic chlorine, which can catalyze the destruction of ozone. One chlorine atom, it is now estimated, can cause the destruction of at least 100,000 ozone molecules in the one or two years before the chlorine forms a hydrogen chloride molecule, HC1, and is carried away by atmospheric moisture. [Pg.595]

The destruction of ozone requires atomic chlorine produced by sunlight ... [Pg.178]

HCFC Ultraviolet Absorption Spectra. While the presence of hydrogen atoms makes HCFCs susceptible to OH attack in the troposphere, this reaction is sufficiently slow that some transport of the HCFCs into the stratosphere will occur. For example, the tropospheric lifetime, with respect to reaction with OH, of CF3CCI2H is approximately 1.6 years, whereas that of CF2CICH3 is about 25 years [65]. Once the HCFCs have reached the stratosphere, their photolysis by ultraviolet (UV) radiation in the range 190 to 230 nm releases active chlorine to participate in ozone destruction. The photolysis is in competition with chemical reaction of the HCFCs with stratospheric OH radicals and 0( D) atoms therefore, measurements of the UV absorption cross sections are required to ascertain the ozone-depletion potentials of the HCFCs. [Pg.49]

Molina, Mario J., and F. Sherwood Rowland. Stratospheric Sink for Chlorofluoromethanes Chlorine-Atom Catalyzed Destruction of Ozone. Nature 249 (1974) 810-112. This is the article that first predicted destruction of the ozone layer by chlorofluorocarbons (CFCs). [Pg.310]

Reduction of ozone is greatly enhanced over the poles by a combination of extremely low temperatures, decreased transport and mixing, and the presence of polar stratospheric clouds that provide heterogeneous chemical pathways for the regeneration of atomic chlorine. The resulting rate of O3 destruction is much greater than the rate at which it can be naturally replenished. [Pg.1191]


See other pages where Ozone Destruction by Atomic Chlorine is mentioned: [Pg.7]    [Pg.7]    [Pg.7]    [Pg.7]    [Pg.159]    [Pg.357]    [Pg.731]    [Pg.595]    [Pg.1577]    [Pg.105]    [Pg.407]    [Pg.188]    [Pg.282]    [Pg.845]    [Pg.595]    [Pg.286]    [Pg.674]    [Pg.677]    [Pg.204]    [Pg.198]    [Pg.329]    [Pg.331]    [Pg.209]    [Pg.358]    [Pg.31]    [Pg.94]    [Pg.120]    [Pg.151]    [Pg.139]    [Pg.177]    [Pg.193]    [Pg.598]    [Pg.184]    [Pg.198]    [Pg.213]    [Pg.152]   


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Atomic chlorine

Atomization by atomizer

By chlorination

Chlorine destruction

Chlorine ozone destruction

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