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Chemical Kinetics

Question
CBSEENCH12006249

For the reaction:
NO2(g) + CO (g) → CO2(g) + NO(g)
the experimentally determined rate expression between 440 K is rate = k[NO2]2. What mechanism can be proposed for the above reaction?

Solution
NO2(g) + CO(g) → CO2(g) + NO(g)
The mechanism proposed for the above reaction involves two steps:

Step. 1.
 
 NO2(g) + NO2(g) slow NO(g) + NO3(g)


Step. 2.
NO3(g) + CO(g) fast  CO2(g) + NO2(g)


Overall reaction:
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NO2(g) + CO(g)     CO2(g) + NO(g)

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As we have given that  rate = k[NO2]2
 
Since concentration of CO(g) is not involved in the rate expression, so the overall rate of reaction is determined by the intermediate formation of NO3(g) i.e., Step 1.