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Topic: Decomposition of Ozone in the atmosphere  (Read 741 times)

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Offline Win,odd Dhamnekar

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Decomposition of Ozone in the atmosphere
« on: September 07, 2024, 04:04:05 PM »
Consider this scenario and answer the following questions: Chlorine atoms resulting from decomposition of chlorofluoromethanes, such as CCl2F2,catalyze the decomposition of ozone in the atmosphere. One simplified mechanism for the decomposition is:

O3 [itex]\xrightarrow{\text{sunlight}}[/itex] O2 +O
O3 + Cl  :rarrow: O2 + ClO
ClO +O  :rarrow: Cl + O2
(a) Explain why the Chlorine atoms are catalyst in the gas-phase transformation :
2O3 :rarrow:  3O2 ?

(b)Nitric oxide is also involved in the decomposition of ozone by the mechanism:

O3[itex]\xrightarrow{\text{sunlight}}[/itex] O2 + O
O3 + NO  :rarrow: NO2 + O2
NO2 + O  :rarrow: NO + O2

Is NO catalyst for the decomposition of ozone? Explain your answer.

My answer:

 (a) Why are chlorine atoms catalysts in the gas-phase transformation?

Chlorine atoms act as catalysts in the decomposition of ozone because they facilitate the reaction without being consumed in the overall process. The mechanism is as follows:

1. O3 + Cl → O2 + ClO
2. ClO + O  :rarrow: Cl + O2


In this cycle, chlorine atoms react with ozone to form chlorine monoxide (ClO) and oxygen (O2). The ClO then reacts with atomic oxygen (O) to regenerate the chlorine atom and produce more oxygen (O2). Since the chlorine atom is regenerated and can participate in multiple cycles, it acts as a catalyst.

 (b) Is NO a catalyst for the decomposition of ozone?

Yes, nitric oxide (NO) is a catalyst for the decomposition of ozone. The mechanism is:

1. NO + O3 → NO2 + O2
2. NO2 → NO + O(under sunlight)
3. NO + O → NO2


In this process, NO reacts with ozone to form nitrogen dioxide (NO2) and oxygen (O2). Under sunlight, NO2 dissociates back into NO and atomic oxygen (O). The NO is regenerated and can continue to catalyze the decomposition of more ozone molecules, making it a catalyst.

« Last Edit: September 07, 2024, 06:58:17 PM by Win,odd Dhamnekar »
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