Why Ozone layer is at the top?

Molecular weight of Ozone is 48.

It is heavier than Oxygen and Nitrogen .

Then why Ozone goes above Nitrogen and Oxygen ?

P.J.LAKHAPATE
plakhapate@rediffmail.com

 

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plakhapate, you asked a similar question in this thread. The vertical composition of the atmosphere has very little to do with the molecular weights of the gases that compose the atmosphere. A much better question is why isn't the ozone uniformly distributed throughout the atmosphere as are most other gases?

The answer is that ozone is a very active chemical. Ozone doesn't last long enough in the atmosphere to mix like less active gases do. An ozone molecule will interact with something else in the atmosphere in a fairly short time period. This something else might be a high-energy photon or some chemical such as a hydrocarbon or a flourocarbon. Ozone only exists only in those parts of the atmosphere where it is created. This is either very high up in the atmosphere, where ozone is created by very high-energy photons interacting with oxygen, and very close to the surface, where ozone is created by moderate energy photons interacting with pollutants.

 

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If the rate of generation is much higher than rate of destruction and if generation of Ozone is at higher level then it is o.k.(assuming there is no much disturbance)

If this logic is o.k. why water vapours go at the top and remain there as cloud ?

According to me water vapours (mol wt 18) is much lighter than Nitrogen (mol wt 28) and Oxygen (Mol wt 32).

P.J.LAKHAPATE
plakhapate@rediffmail.com

 

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You've been clearly told in both this thread and the other one that molecular weight really has very little, if anything, to do with the mixing of atmospheric gasses. And water vapor does not "go to the top and remain there." Under most conditions, humidity hangs around a few hundred feet from ground level. However, warm air transports HUGE amounts of water vapor far above than. In fact, warm, moist air will override colder, denser air.

Consider this and you can see how your thinking is in error: according to your view, volcanic ash and smoke - being FAR denser than atmospheric gasses - should completely fall out in the immediate vicinity of the volcano. Yet they don't all do that. Much of it can travel hundreds, even thousand of miles from the source.

The primary force that mixes atmospheric gasses is simple Brownian motion - the random movement of molecules. And beyond that, the atmosphere is a VERY dynamic place!!! You seem to be trying to view it as a static column of gas sealed in a very tall pipe. That's far from the case. And not only that, even under those conditions the Brownian motion would keep them mixed rather than allowing them to settle out according to weight - which appears to be what you would expect to happen. Just not true.