AAMC 6 Item 20 (Repulsion vs Volume)

[somuchwater]

So the question is about a gas that has 10 L at ATP and is pressurized to 500 atm . The options are

A) V = 0.020

or B) V > 0.02 L b/c of volumes of gas molecules

or C ) V > 0.02 b/c of repulsions between individual gas molecules..

it's B not C. Why isn't it C? If you pressurize it, ideal volume is 0.02 L but it's not b/c the closer the gas molecules are to each other, the more they will repel each other. The actual answer explanation for B is

"The ideal gas law makes the assumption that molecules have no volume. This assumption is adequate when the gas is at 1 atm but when pressure is increased to 500 atm the volume of the gas molecules is no longer neglible"

This makes no sense to me. I feel like the repulsions are far more important.!

Please help. Thanks!

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[Cawolf]

http://forums.studentdoctor.net/threads/aamc-official-practice-exam-q-a-discussion-threads-rules-of-order.516243/

http://forums.studentdoctor.net/threads/aamc-cbt6-and-6r-official-q-a.516254/

 

[TheRhymenocerous]

Huh I swear this question was on another FL. You're calculating the volume using the ideal gas equation, which assumes low pressure. Now that it's under high pressure, it no longer behaves as an ideal gas, meaning volume of the molecules and intermolecular forces matter. You don't know what those forces are, though, so they might not be repulsive. You might have a gas with attractive forces, in which case your volume would be smaller than predicted. Volume is going to be an issue no matter what.