The catalytic destruction of ozone in the stratosphere...

The catalytic destruction of ozone in the stratosphere occurs via a two-step mechanism where X in the equations below can be one of several different species, including a Cl free radical. Step 1: X + O3 → XO + O2 (slow) Step 2: XO + O → X + O2 (fast) 1. Aircraft in the stratosphere release NO, which catalyzes the destruction of ozone by the mechanism in this problem. Write the mechanism substituting NO appropriately. 2. When the [O3] is 5 x 10^12 molecules/cm^3 and the [NO] is 1.0 x 10^9 molecules/cm^3, what is the rate of ozone depletion? The rate constant, k, for the rate-determining step is 6 x 10^-15 cm^3/molecules-s. In the mechanism for the destruction of O3, which would you expect to have a higher value for the orientation factor (p), Cl or NO as X in step 1? Explain.

Transcript

0:00 All right.

00:01 Here we're writing, we're working with the destruction of ozone.

00:05 Oh, i'm missing some other question.

00:07 The destruction of ozone here.

00:10 This is step two.

00:12 And it's a two -step process.

00:13 We have a slow step where it's an x -reacted ozone to make xo and oxygen.

00:19 And then oxygen is kicked off.

00:20 And then that x -o product can react with a single oxygen, which is critical to the formation of ozone and make oxygen.

00:28 So we're destroying ozone directly as well as undercutting its ability to form new ozone with these x species.

00:36 And also this x species that we're considering is either in o or could also be chlorine.

00:41 And so these chlorine was a big deal in the second half of the 20th century.

00:47 Because cfcs, which were coolants and refrigerants and whatnot, would break apart under dv lights in the stratosphere.

00:55 And release chlorine atoms that would then destroy the ozone.

00:58 And so that's where the ozone hole came about until we dealt with the cfc issue in the late 80s and early 90s.

01:06 And i was still released by plane cell, and so that's still an atmosphere as they fly across the globe.

01:15 So the first one is to write the reaction for n0 for x.

01:20 And so let's go ahead and do that.

01:23 So no is our x plus o3.

01:26 And that's going to make xo.

01:28 Well, our x is n0.

01:30 X0 is n02.

01:33 So we added 1 .0 to our x and our x is n0.

01:36 So we have two oxygens, and that's plus o2.

01:39 And then the second step is n02, plus the single auction makes n o plus o two.

01:47 So now we've had the equation for n o.

01:51 And we have to find the rate of ozone depletion and gives us some values accordingly.

01:56 And so we know that this is slow and this is fan.

02:01 And thankfully the first step is slow, because things are a little easier when the first step is slow, because this is your rate determining step, which means our ozone depletion is going to be essentially the rate of this first step, means as soon as we deplete ozone, this next one happens really fast, and it's not going to affect the rate of the reaction.

02:24 So the only thing we have to consider is this first rate.

02:26 And so that rate for the first equation is going to be rate is equal to k times our o3 times or in o...

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