AAMC 10 Questionz

[Hexon]

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hey guys, having some twubblies wif some pwoblems.
🙂

Q11: would deviations from ideal gas law be observed for gaseous nitrogen at 1 atm and room temp?

i answered yes but for the wrong reasons; i don't understand why room temperature wouldn't affect gaseous nitrogen. doesn't heat cause all them atoms and molecules to vibrate like crazy?

 

[hvairline]

could you post all of the answer choices?

 

[Hexon]

sure, other answer choices were
1) no, cuz both temp. and pressure must increase before any such deviation may occur.
2) no, cuz nitrogen molecules are symmetrical and don't react with each other
3) yes, cuz at this pressure, molecular volume and intermolecular interactions becomes significant.
4) yes, cuz at room temp, molecular volume and intermolecular interactions becomes significant.

the answer is 3) but i don't understand why room temp wouldn't also have as significant an influence over molecular volume and intermolecular interactions.



btw in the biological sciences section, passage II q109; the comparison between two acids, i cant seem to upload the pic i took of the q, but if anyone knows why resonance stabilisation isn't the prime reason for the acidity of compound I, please let me know🙂
also

q118
uridine nucleotides which are incorporated into RNA are sourced from where?😛

and q120
just to clarify; a woman gets all her ova in her lifetime between her formation as a foetus after fertilisation and before birth? does this mean meiosis II doesn't start for her until puberty?

 

[MT Headed]

Q11: would deviations from ideal gas law be observed for gaseous nitrogen at 1 atm and room temp?

Q11 asks if you would expect deviations at room temperature and 180 GPa 😱 of pressure. The answer is yes, because you expect deviations from ideal gas behavior at high pressure and low temp.

 

[MT Headed]

and q120
just to clarify; a woman gets all her ova in her lifetime between her formation as a foetus after fertilisation and before birth? does this mean meiosis II doesn't start for her until puberty?

One egg a month undergoes (finishes, really) meiosis I during puberty.
Meoisis II doesn't finish until/unless the egg is fertilized.

 

[MT Headed]

q118
uridine nucleotides which are incorporated into RNA are sourced from where?😛

Like all nucleotides, they are built in the cytoplasm, and float around aimlessly. Due to brownian motion some wind up in the nucleus. The nucleus is where ribonucleotide monomers are assembled into RNA polymers through the process of transcription.

 

[MT Headed]

btw in the biological sciences section, passage II q109; the comparison between two acids, i cant seem to upload the pic i took of the q, but if anyone knows why resonance stabilisation isn't the prime reason for the acidity of compound I, please let me know🙂

Resonance stabilization would apply to both molecules. The question is asking why molecule 1 is more acidic than molecule 2. You need a reason that applies to molecule 1 and doesn't also apply to molecule 2.

Intramolecular hydrogen bonding is pretty whack. I was surprised that the MCAT covered this topic at all. Here's another problem to check your grasp of intramolecular hydrogen bonding:

What conformation of 1,2-ethandiol is most stable?
A) totally eclipsed
B) gauche
C) eclipsed (but not totally eclipsed)
D) anti

It may help to build a molecular model.

 

[Hexon]

Resonance stabilization would apply to both molecules. The question is asking why molecule 1 is more acidic than molecule 2. You need a reason that applies to molecule 1 and doesn't also apply to molecule 2.

Intramolecular hydrogen bonding is pretty whack. I was surprised that the MCAT covered this topic at all. Here's another problem to check your grasp of intramolecular hydrogen bonding:

What conformation of ethandiol is most stable?
A) totally eclipsed
B) gauche
C) eclipsed (but not totally eclipsed)
D) anti

It may help to build a molecular model.

is it anti?😛 i reasoned ethylene glycol/ethandiol like most molecules would be most stable in the trans form, as opposed to cis.

thanks for your really helpful answers btw, and for all your help in this forum🙂

 

[MT Headed]

Well, most people would think it would be anti, but now take intra-molecular hydrogen bonding into account. You have an OH group, and another OH group nearby...

 

[Hexon]

Well, most people would think it would be anti, but now take intra-molecular hydrogen bonding into account. You have an OH group, and another OH group nearby...

hmmm, i drew the newman projection in the anti conformation; what am i missing with the intramolecular hydrogen bonding? would it be gauche?
how would the OH groups influence the h-bonds nearby other than hog all them electrons?😛

 

[MT Headed]

hmmm, i drew the newman projection in the anti conformation; what am i missing with the intramolecular hydrogen bonding? would it be gauche?
how would the OH groups influence the h-bonds nearby other than hog all them electrons?😛

Yup, gauche. It won't go totally eclipsed because the O's will repel each other, but in a gauche conformation the two OH groups can hydrogen bond to each other somewhat incestuously. It's real easy to see this if you have a molecular model kit.

This is kind of a classic trick question in ochem and not the sort of thing I would expect to see tested on the MCAT ("the MCAT tests rules, not exceptions"), but then along comes AAMC10 q109. The sneaky devils.

 

[Hexon]

Yup, gauche. It won't go totally eclipsed because the O's will repel each other, but in a gauche conformation the two OH groups can hydrogen bond to each other somewhat incestuously. It's real easy to see this if you have a molecular model kit.

This is kind of a classic trick question in ochem and not the sort of thing I would expect to see tested on the MCAT ("the MCAT tests rules, not exceptions"), but then along comes AAMC10 q109. The sneaky devils.

gauche, nice🙂

when i picture it 3 dimensionally in my head it makes sense🙂 thanks