PT21.S2.Q19 - spectroscopic analysis has revealed - super hard NA q.

karenkaren

Hello,

This is an NA question that I have been trying to grasp. It's REALLY hard.

I will explain how I can justify the to myself and I would be so grateful if anyone wants to chime in and add any additional analysis.

The stimulus -
CTX: There is frozen nitrogen, methane, and carbon monoxide on the surface of Pluto, which vaporize to make Pluto's atmosphere.

P: The proportion of each gas in Pluto's atmosphere results how readily the gas vaporizes.

C: Pluto's atmosphere is made of nitrogen, methane, and carbon monoxide gas, listed from greatest to lowest proportion.

The correct answer states that there is no frozen substance (let's call it X) on Pluto that vaporizes more readily than methane but less readily than carbon monoxide. In other words there is no gas X in the atmosphere of which there is more than methane and less than carbon monoxide. The negation would read like this: C > X > M , there is a fourth gas in the atmosphere and there is more carbon monoxide than methane (if I understand correctly).

I think my issue at first was that I did not read the conclusion to say there were only three gases in the atmosphere and no others; I suppose stating "the components are..." does imply that. So, if there was a fourth gas in the atmosphere, there are not three, as the conclusions claim. Moreover, with the CA negated, there would be more carbon monoxide than methane, which wrecks the argument. This seems to be an example of a really bare minimum NA, that makes you go "doi."

I chose (D), which states that nitrogen is only found in the atmosphere if it is also found as ice on the planet's surface. It's useless to the argument. Natm --> Nps ; /Nps --> /Natm. Neither of these statements reveal anything new or relevant about the situation.

Thanks in advance for any input!

AllezAllez21

I think you've pretty much nailed the analysis of the question. When I went through it I also wasn't entirely clear on those three gases being the only components of the atmosphere, but as soon as the answer popped up, I realized that must be the case.

DumbHollywoodActor

It's not that there are no other gases. This question leans on the distinction between proportion and quantity. A proportion or ratio tells us the relationship between items without telling us the quantity or value of those things. For example, if an ice cream shop always carries a proportion of 2 popsicles for every 3 snow cones, we have no idea how many snow cones or popsicles the ice cream shop has until we know the quantity of the other.

It's that the PROPORTION of the gas relative to all other gases is determined by how readily that gas vaporizes from ice to gas. There can be other gases present, but in order for the conclusion about the QUANTITY of the gases to follow, Nitrogen needs to be 1st (Gold Medal) in readily vaporizing on Pluto, carbon monoxide needs to be 2nd (Silver Medal) in readily vaporizing on Pluto, and methane needs to be 3rd (Bronze Medal) in readily vaporizing on Pluto.

Answer C makes sure that methane wins the bronze medal. If we negate it, then some other gas wins the bronze and then it's impossible (given the direct relationship between proportion of gas and how readily the gas vaporizes) for methane to be the third highest abundant (QUANTITY) gas.

Hope this helps.

karenkaren

Thanks @DumbHollywoodActor for the very helpful answer. It is hence the order of the quantities of the gases that is the crux of the argument. The gold/silver/bronze medal analogy is great.