AAMC FL 1&2 Chem/Phys

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bbiebelberg
Posts: 19
Joined: Thu Jan 09, 2020 8:28 pm

AAMC FL 1&2 Chem/Phys

Post by bbiebelberg » Tue Jun 09, 2020 7:10 pm

Hello! I have a few questions from the Chem/Physics sections of AAMC FL 1 and 2...
Thank so much.

### AAMC FL 1 ###

Chem/Physics
>Question 10
I don’t really understand this. What’s a good general approach to this sort of question? I know why choice C is wrong — that is not participating in the reaction. In terms of eliminating choices A and C, is the idea that the acidic H in acetic acid and the alcoholic H in ethanol could both be de-protonated by the environment before the reaction of interest actually takes place? Or is there a better approach to arrive at choice D?

>Question 45
I wasn't able to follow this derivation clearly. Are you able to provide a little more guidance with the correct way to approach this?


### AAMC FL 2 ###

Chem/Physics
>Question 25
I know that the Venturi effect says a narrower tube is associated with lower pressure. But I don’t understand how the answer to this question is an application of that principle.

>Question 26
Why do G-C base pairs have stronger pi-stacking interactions than A-T base pairs?

>Question 36
I guessed coordinate ionic here, but I realize now there’s no such thing, and that coordinate bonds are covalent. Perhaps my question then ought to be, how to tell the difference between an ionic bond and a coordinate bond such as in the molecule here?

>Question 53
Looks like the solution uses the Work-KE theorem. I tried to solve by calculating work as force times distance, using the elastic force F=kx. So I calculating W = (kx)(x) to get 8J. I didn’t multiply by 1/2 as is done in the Work-KE theorem. Why is Work-KE correct here but the standard work equation isn’t?
NS_Tutor_Nancy
Posts: 47
Joined: Wed May 27, 2020 7:25 pm

Re: AAMC FL 1&2 Chem/Phys

Post by NS_Tutor_Nancy » Thu Jun 18, 2020 9:51 pm

Hello!

For AAMC FL #1:
Q10: You are exactly right, choice C can be eliminated because the carbonyl oxygen does not participate in this reaction. Choices A and B can be eliminated because hydrogens can be exchanged with the solution/other reacting species prior to the reaction, whereas the hydroxyl oxygen will not move around except in the specific reaction in question.
Q45: Remember that the thin lens equation says 1/f = 1/do + 1/di, so you can flip this around to 1/di = 1/f – 1/do = 1/f – 1/3f = 3/3f – 1/3f = 2/3f. Since 1/di = 2/3f, di = 3f/2. The ratio of image height to object height is the same as the ratio of image distance to object distance (think about magnification formula) so 3f/2 : 3f is the ratio the question is looking for. 3f/2 divided by 3f gives an answer of 1/2.

For AAMC FL #2:
Q25: The venturi effect refers to the reduction in fluid pressure (in this case the fluid is a gas) when flowing through a constricted section of a pipe/tube/etc. So the air flowing through the tube is at a lower pressure than the surrounding air. Air will move from the area of higher pressure to the area of lower pressure in through the slits.
Q26: Pi stacking refers to noncovalent interactions between aromatic rings, so it is based on how the aromatic rings of the nitrogenous bases align in DNA.
Q36: In coordinate covalent bonding, one atom donates electrons and the other atom does not input anything. In an ionic bond, one species loses electrons and the other gains electrons (attraction between resulting cation and anion creates ionic bond).
Q53: This one is easier to explain with a picture, try looking up a work on spring graph. Yes, work = force * displacement, but the key here is that force includes displacement in the equation (F = kx). If you look at a work on spring graph with force on the y axis and displacement on the x axis, you’ll see that the force increases with distance, creating a triangle area under the curve which is why you end up with work = (1/2)kx^2.

I hope this helps!
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