NO3

[McKenna_4A]

Why isn't NO3 included in the overall equation for O2 ---> ozone if it is used as a reactant?

[Caitlyn Tran 2E]

I'm not sure what the context for this question is, but usually something would not be included in the overall equation if it is a catalyst or an intermediate. Hope this helps!

[Ryan Yee 1J]

NO is a catalyst, and since it is present at the start and end of the reaction, then it is not written in the expression.

[chrisleung-2J]

Yes, it is correct that because NO3 is a catalyst it would not be included in the overall rxn equation.

[CameronDis2K]

If any compound is not present in the overall reaction, then it can be considered an intermediate (as it cancels out in the reactants and products). Therefore, NO3 can be considered an intermediate.

[Patrick Ngo 2J]

The O2 --> O3 reaction has three steps. We see that 1 NO is used as a reactant in the first step, and 1 NO is generated through the second step (essentially, NO is unused). Therefore, NO is acting as a catalyst: It is not consumed by the reaction, but it is necessary to get the reaction going (without NO, step 1 will not occur). We do not include NO, a catalyst, in the overall reaction because it is cancelled out, and we will not include it in the rate law either.

It is also important to distinguish NO being a catalyst and not an intermediate. Although a catalyst and intermediate both are not included in an overall reaction, they are not included for different reasons (catalyst is used, then reproduced so it still exists by the end. intermediate is produced, then used, so it does not exist by the end).

Hope this helps!

[Russell Ahmed 2K]

NO is present in the first step of this reaction mechanism - it is a catalyst that helps "jump start" the reaction (by lowering the activation energy). It is then consumed, then reformed in a later step. When you add these steps together for the overall reaction, the NO will cancel out (as it is present in the same molar ratio on each side of different steps in the mechanism). Catalysts, like intermediates, are never present in the overall reaction nor should they be included in the rate law.