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AAMC Question- Ideal Gas
Chloe_2125
#1 Posted : Friday, June 18, 2021 5:38:43 AM
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Hi,

In the AAMC full length I came across this question. I don't understand why C is the answer and not D. Would you be able to help me differentiate between these two answers?


The term “ideal gas” refers to a gas for which certain assumptions have been made. Which of the following is such an assumption?

A.The law PV = nRT2 is strictly obeyed.
B.Intermolecular molecular forces are infinitely large.
C.Individual molecular volume and intermolecular forces are negligible.
D.One gram-mole occupies a volume of 22.4 L at 25°C and one atmosphere pressure.

Thank you :)
INSTR_Katrina_128
#2 Posted : Friday, June 18, 2021 10:14:23 PM
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Hi Chloe!

This one is really sneaky. 😯

D is ALMOST true... but they're messing with you. One mole of an ideal gas occupies 22.4 L at STP -- standard temperature and pressure, which is 0°C and 1 atm, NOT 25°C. That's why D is wrong in this case. But, we usually use 22.4 L (or 22 L, let's be honest) because we love to take advantage of rounding hehehe PROVIDED that our gas temperatures are close to 0°C and the MCAT answers are "far enough apart".

Now, why is C correct?

Some of the fundamental assumptions of the ideal gas law include:

- That the ideal gas itself is made up of particles so small that they don't even take up any volume.

- That the ideal gas itself is made up of particles that are so far apart from each other that they never see each other and therefore, do not interact. Social distancing before it was necessary.

Therefore, C is the best answer.

Chloe_2125
#3 Posted : Saturday, June 19, 2021 5:44:24 AM
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Thank you for the thorough explanation, I really appreciate it :)
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