The concentration of H₂O in the stratosphere is about 5 ppm. It undergoes photodissociation according to: H₂O(g) → H(g) + OH(g)
(c) The hydroxyl radical, OH, can react with ozone, giving the following reactions:
OH(g) + O₃(g) → HO₂(g) + O₂(g)
HO₂(g) + O(g) → OH(g) + O₂(g)
What overall reaction results from these two elementary reactions? What is the catalyst in the overall reaction? Explain.

Question

The concentration of H₂O in the stratosphere is about 5 ppm. It undergoes photodissociation according to: H₂O(g) → H(g) + OH(g)

(c) The hydroxyl radical, OH, can react with ozone, giving the following reactions:

OH(g) + O₃(g) → HO₂(g) + O₂(g)

HO₂(g) + O(g) → OH(g) + O₂(g)

What overall reaction results from these two elementary reactions? What is the catalyst in the overall reaction? Explain.

Accepted Answer

Hello everyone today. We have the falling problem shown in the mechanism below is the catalyzed decomposition of hydrogen peroxide, determine the catalyst or catalysts and the reaction intermediate or intermediates. So first, let's define what each of these mean. So simply put a catalyst is a compound that is used in the first step. So it's used in the first step and then it is regenerated in the last step generated in the last step. And intermediate. On the other hand, an intermediate is produced in the first step and used In the 2nd step. So they are essentially polar opposites. And so we have the reaction as it is. So we have our step one and we have step two. So we need to find the overall reaction. And so what is that going to look like? We're going to add up anything that is on the same side and we're going to get rid of anything that is on the opposite side. So, for example, we have a peroxide and step one on the left and a peroxide on the left. In the second step. So that's going to give us two peroxide. So two H 202. If we notice anything else, we know that we have to bromide ions on the left here and we also have it on the right hand side of our arrow in step two. So we can cross out our bromide ions. If we look closer, we can also see that we have two hydrogen or two protons on the left of our step one and we have two protons on the right of our step two. So those can get crossed out as well. Lastly, if we look on the left of our step two, we have our bro mean, but we also have broken on the right of step one. So essentially we only have one reactant, which is going to be our two peroxide. And there are two products are going to be two waters, two H 20 and then the one oxygen gas. So, for this overall reaction, if we were to determine the catalysts, so the catalyst based on what we just solve for, they're going to be our bromide and our hydrogen plus or protons. And so why is that? That is because these two are used in the first step and then they are regenerated in the last step, or the second step here. And so if we were to look at our intermediate or intermediate, Intermediate or intermediates, this is going to be our bro mean, RBR two. And so this is because our bro mean, is produced In the 1st step. So, it's a product in our first step and used in the second step or the last step. And so, if we look at option C option C is not correct because these are not all catalysts. Right. The former brahmi in hydrogen plus serves as a catalyst that's used in the first step, regenerate in the second step, I just said before, and the latter, which is bro mean, is going to be an intermediate, which is produced in the first step and used in the second step. Option D is also wrong because this mechanism has both catalysts and intermediates, and so between A and B, the best option is going to be answer choice B. As you said before, and with that, we've answered the question overall, I hope this helped, and until next time.

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Verified Solution

Key Concepts

Photodissociation

Elementary Reactions

Catalysis