#26 - Concept Reference, Must Be True

[Administrator]

This explanation is still in progress. Please post any questions below!

[ChicaRosa]

I don't understand why D is correct?

I believe the question type is a global reference, strengthen question. I read the second paragraph where it addresses chlorine and it's interaction with the ozone layer and was stuck between C and D and ended choosing C as a quick guess.

Is C wrong because even if we know how a chemical would react with chlorine it wouldn't help replace the CFC?

Is D correct because if we tested a chemical to see if it has an element common with chlorine then it would help us to determine to use it or not?

Thanks!

[David Boyle]

I don't understand why D is correct?

I believe the question type is a global reference, strengthen question. I read the second paragraph where it addresses chlorine and it's interaction with the ozone layer and was stuck between C and D and ended choosing C as a quick guess.

Is C wrong because even if we know how a chemical would react with chlorine it wouldn't help replace the CFC?

Is D correct because if we tested a chemical to see if it has an element common with chlorine then it would help us to determine to use it or not?

Thanks!

Hello,

It is a "Must be true, concept reference" question. C is wrong because "reacting with chlorine" isn't the issue; the issue is that chlorine is damaging, so we wonder how a chemical might imitate chlorine or not. And that's why D is right, because chlorine and its effects are crucial.

David

[jw190]

Hello everyone,

This question caused a lot of problems for me as well. I was initially stuck between D and E, and chose E. I also picked E again when blind reviewing. My reasoning is that if the chemical does not break down into its component parts when subjected to UV, how could it cause any damage to the ozone? The breakdown because of UV was a key part of the passage. In fact, if the CFCs did not break down because of UV, it seems possible that they wouldn't cause damage to the ozone in the first place.

I struggled in chemistry, but I know that Chlorine is an element all by itself. As long as the chemical being tested does not contain the element chlorine, I can't see how it would matter. I've seen and been tricked by LR questions like this before (the one about male / female cats and getting some disease rings a bell).

This one is tough! Thanks for any help!

[Kristina Moen]

Hi jw,

This one was a tough question! The question asks about designing a test for a chemical other than CFCs, so what I'm looking for is a test that will determine whether that chemical acts like CFCs or not.

The second paragraph describes the process by which CFCs harm the ozone. It can be very helpful to break it down (no pun intended!) into parts, so you can better understand each step.
1) CFCs are released into the lower atmosphere (for example, by spraying aerosol hairspray).
2) The CFCs slowly move upward to the stratosphere (they defined "stratosphere" for us earlier in line 6).
3) The CFCs are subject to UV rays in the stratosphere, which break it down into its elements.
4) ONE of those elements, chlorine, is devastating to the ozone.
5) The chlorine not only destroys the ozone, but the reaction causes it to regenerate (this is horror movie stuff!).

So as you can see, it's not breaking down into elements that's so bad. It's one element that is a result of the breakdown - namely, chlorine. We're not told anything about the other elements that make up CFCs.

You're right that it seems like if the CFCs weren't broken down by the UV rays, it wouldn't be as harmful. However, what if we just shot straight chlorine into the stratosphere? Seems like the chlorine is the real culprit here!

[jw190]

This one was a tough question! The question asks about designing a test for a chemical other than CFCs, so what I'm looking for is a test that will determine whether that chemical acts like CFCs or not.

You're right that it seems like if the CFCs weren't broken down by the UV rays, it wouldn't be as harmful. However, what if we just shot straight chlorine into the stratosphere? Seems like the chlorine is the real culprit here!

Thanks for the reply! Hmm that's a good point. I never considered the possibility of shooting chlorine by itself into the atmosphere. In that case I guess UV breakdown would be irrelevant!

As far as the correct answer goes, however, does sharing a property necessarily mean that a chemical will act like chlorine? I guess since chlorine is an element all to itself, similar elements to chlorine broken down in the ozone could act like it chlorine. Seems like a question where basic chemistry knowledge could come in handy.

Based on your breakdown, I definitely see how it's better than my answer, but still seems like not a great answer by itself. Frustrating!

Thanks again!

[Kristina Moen]

The question asks about which test would be "most useful." Keep in mind that you are not looking for a test that's going to yield with certainy the answer to the question of whether the chemical could replace CFCs without harming the ozone.

Sometimes you really have to go with the best answer, even if you feel like you could argue your way out of it!

[ninamichelle]

I chose (C) as the correct answer. Wouldn't determining how the replacement-CFC chemical interacts with chlorine be important, since chlorine atoms are regenerated when they interact with ozone, and the CFCs accumulated in the atmosphere could take decades to cease depletion of the ozone layer (meaning, as I understood it, those chlorine atoms are still alive and kicking up in the stratosphere)? If the new chemical further encouraged the regeneration of chlorine in the ozone, wouldn't this worsen the situation?

[AthenaDalton]

Hi Nina,

You raise a really good point -- scientists should consider how any additional pollutants released into the atmosphere interact with existing chlorine chemicals.

However, (D) is a better answer than (C). Since we know from the passage that chlorine causes a catastrophic chain of effects once it reaches the upper atmosphere, the top priority for scientists in designing any replacement for CFCs would be to consider whether the chemicals will break down into chlorine or combine to form chlorine once released into the atmosphere. It's a top priority to ensure that whatever CFCs are replaced with will no produce the exact same problem.

Only once scientists are sure that the CFC replacement will not turn into chlorine can they start considering secondary effects, like how the replacement chemical will interact with existing chlorine molecules in the atmosphere.

This question is a case of picking the better of two answers.

I hope this helps clarify things for you. Good luck!

Athena Dalton

[RajPatel]

Sorry to revive another old thread, but I'm having trouble wrapping my head around answer choice (B) being incorrect. The explanation behind this being incorrect is because ozone is in the upper atmosphere, not the lower atmosphere. While the passage states that the ozone layer is in the stratosphere, I googled "lower atmosphere," with some results indicating that this is where the lower stratosphere is. This contradicts with the reasoning of (B) being incorrect.

Can someone help me out on this? It was to my understanding that the LSAT requires no outside/factual knowledge, but whether the ozone layer is in the lower atmosphere or upper atmosphere sounds like factual knowledge, and the passage does not delineate that the ozone layer being in the stratosphere is the upper atmosphere, not the lower atmosphere.