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    I'm doing AQA A2 Chemistry, and I was revising order of reaction and saw on the specimen paper the following question:

    When NO and O2 react at a constant temperatue the rate equation is rate = k [NO]2 [O2].

    Using the rate equation, a mechanism was suggested for the reaction consisting of the two steps:

    (1) NO + NO --> N2O2
    (2) N2O2 + O2 --> 2NO2

    Which did scientists suggest was the rate-determining step?

    Now I managed to guess when doing this as a mock, but I still don't understand how the answer is the second step. Can anyone explain how you can make this mechanism by looking at the rate equation, and also how you know which is the rate-determining step?

    Thanks in advance.

    Ok, the rate determining step is the slowest one. And the molecules in the rate equation take part in the rate stage. If its a reactant squared that means 2 molecules of it take part in the rate determining step.

    So you know the rate determining step will take 2 molecules of NO (or what they have bonded in a quick step to make in this step) and one of O2 so the second of those two steps is the rate determining step.
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