What is the catalyst in this reaction mechanism?CCl2F2   -->  CClF2   + Cl Cl  + O3   -->  ClO  +  O2 ClO  + O  -->  Cl  +  O2 At first I thought it was Chlorine, but it...

What is the catalyst in this reaction mechanism?

CCl2F2   -->  CClF2   + Cl

Cl  + O3   -->  ClO  +  O2

ClO  + O  -->  Cl  +  O2

At first I thought it was Chlorine, but it doesn't cancel out in the net reaction. 

I got this for the net reaction: 

CCl2F2 + O3 + O --> CClF2 + Cl + 2O2

I'm so confused, please help!

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ncchemist | eNotes Employee

Posted on

You have the correct reactions written for the depletion of ozone by CFC's (chlorofluorocarbons).  A CFC can produce a chlorine radical.  This radical will react with an ozone molecule to produce ClO and molecular oxygen (O2).  The ClO can then react with an oxygen radical in the atmosphere to produce another O2 molecule and regenerate the chlorine radical.  So the chlorine radical can keep being regenerated to keep on breaking down additional ozone.  This is the true danger with CFC's; the destruction of ozone is a self-sustaining cycle because the chlorine radical is regenerated and reused over and over.  So a single CFC molecule to destroy many, many molecules of ozone.

So what is the catalyst here?  You actually don't have it written down.  The breakdown of a CFC to produce a chlorine radical is not a spontaneous process.  It requires UV radiation from the sun.  The oxygen radical in the third equation also requires sunlight to break down an O2 molecule into 2 oxygen radicals.  So the catalyst for this process is UV radiation from the sun.

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