AAMC CBT8 and 8R OFFICIAL Q&A

[Vihsadas]

This is the official Q&A thread for AAMC CBT8 and 8R.

Please post ONLY questions pertaining to AAMC CBT8 and 8R.
Out of respect for people who may not have completed the other exams, do not post questions or material from any other AAMC exam.

Please see this thread for the rules of order before you post.

Good luck on your MCAT!

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[TypeSH07]

#22 on physical sciences. It says that the molar solubility of M(OH2) is S mol/L. I got the question right b/c I set up the Ksp value as (M)(2OH)^2 but I was confused what it mean when it defined the molar solubility as S. Is that just the concentration of each product? Thanks.

 

[BerkReviewTeach]

#22 on physical sciences. It says that the molar solubility of M(OH2) is S mol/L. I got the question right b/c I set up the Ksp value as (M)(2OH)^2 but I was confused what it mean when it defined the molar solubility as S. Is that just the concentration of each product? Thanks.

Yeah, S represents the salt concentration when saturated. We normally use the letter x to repsresent molar solubility. They probably wanted to twist the typical approach a little, so that people who straight memorize would have to think a bit.

 

[TypeSH07]

Can anyone explain #34 on the PS section. I thought the resistors looked like they are in series, but based on the answer choice I don't think that is the case. What are the half separations that extend out from I3 and I2? Does that have an effect on how you interpret the circuit?

 

[RySerr21]

Can anyone explain #34 on the PS section. I thought the resistors looked like they are in series, but based on the answer choice I don't think that is the case. What are the half separations that extend out from I3 and I2? Does that have an effect on how you interpret the circuit?

hmmm i never had a question like that on mine! my #34 was about insulators and conductors.

 

[TypeSH07]

OH I forgot to mention this was on the paper version not the CBT! That's probably why.

 

[BerkReviewTeach]

OH I forgot to mention this was on the paper version not the CBT! That's probably why.

Are you sure it's AAMC 8, because on the paper version I was referencing, I also have the same question that ryserr was referring to.

 

[TypeSH07]

Yes, but it's not 8R. Maybe thats why.

 

[sicboy188]

so HCl conducts electricity? NO idea.. can anyone explain to me how this works?

 

[sicboy188]

one more question...

after reading the explanation for this question, i noticed a little ambiguity (IMO) in the question stem.

is the 10-m incline plane 10-m of the ground? First time i read it, i assumed the 10-m referred to the length of the plane. But the explanation seems to allude otherwise.

 

[TypeSH07]

Maybe b/c it's electrolytic and will fully dissociate?

I got the answer based on what the passage gave me though so didn't really think about that.

 

[TypeSH07]

one more question...

after reading the explanation for this question, i noticed a little ambiguity (IMO) in the question stem.

is the 10-m incline plane 10-m of the ground? First time i read it, i assumed the 10-m referred to the length of the plane. But the explanation seems to allude otherwise.

Yea the question was pretty ambiguous in the wording but I just assumed the same distance. I just thought a= gsintheta and since it's at an incline the acceleration would be less than that of g, which would increase the time it took over the "same distance".

 

[RySerr21]

so HCl conducts electricity? NO idea.. can anyone explain to me how this works?

no no. its saying " somebody incorrectly concluded that HCl was ionic. which of the following may have lead this person to believe that?"

its a crappily worded question. they are basically saying "which of the following describes an ionic compound." the only one that correclty describes something that is ionic is the that says "A 1M solution conducts electricity"

it took me like 5 min to figure out what the hell they were asking. its quesitons like these that make me despise the MCAT. just ask which of the following describes an ionic compound. jesus.

 

[sicboy188]

no no. its saying " somebody incorrectly concluded that HCl was ionic. which of the following may have lead this person to believe that?"

its a crappily worded question. they are basically saying "which of the following describes an ionic compound." the only one that correclty describes something that is ionic is the that says "A 1M solution conducts electricity"

it took me like 5 min to figure out what the hell they were asking. its quesitons like these that make me despise the MCAT. just ask which of the following describes an ionic compound. jesus.

wow.. thanks. but seriously, eff this question.

 

[thierryhenry]

Yes I agree that Question was poorly worded and bs

 

[Kaustikos]

BS 101 and 102.

I was completely thrown off by that and was wondering if someone can tell me how to figure these out? I believe this was asked before but I could not find it so I figured I would bring it here.

Kinetics - fast as possible and not caring about stability
thermo - stability, not speed and will thus have the highest melting point.

But I'm dumbfounded by the questions. Any review books/questions that can help better familiarize myself with it?

 

[BloodySurgeon]

To think of it in easier terms:
kinetic product- lower activation energy, therefore faster, and less heat needed
thermodynamic product- final energy lvl is lower therefore more stable, but higher activation energy and therefore longer to produce.

 

[happygirl]

BS 110

Hypertension can be caused by increased activity of smooth muscles b/c that would cause vasoconstriction and increase resistance. OK, I get that and ended up choosing that answer. But, why wouldnt increased activity of the cardiac muscle not be a right answer too? Wouldn't increased cardiac activity cause an increase in rate of flow of blood thereby increasing cardiac output?

thanks

 

[Kaustikos]

BS 110

Hypertension can be caused by increased activity of smooth muscles b/c that would cause vasoconstriction and increase resistance. OK, I get that and ended up choosing that answer. But, why wouldnt increased activity of the cardiac muscle not be a right answer too? Wouldn't increased cardiac activity cause an increase in rate of flow of blood thereby increasing cardiac output?

thanks

The passage made a connection between hypertension and blood vessels. That takes out the cardiac muscle completely. The question was basically asking if you knew the type of muscle that makes up blood vessels.

 

[happygirl]

The passage made a connection between hypertension and blood vessels. That takes out the cardiac muscle completely. The question was basically asking if you knew the type of muscle that makes up blood vessels.

So, its not that increasing cardiac muscle activity wouldn't cause hypertension, it's just that for this passage, the focus is on the blood vessels and so the most appropriate answer for this particular passage and question is smooth muscle (even though cardiac was an answer option)?

 

[Kaustikos]

So, its not that increasing cardiac muscle activity wouldn't cause hypertension, it's just that for this passage, the focus is on the blood vessels and so the most appropriate answer for this particular passage and question is smooth muscle (even though cardiac was an answer option)?

Yeah.

Therefore, an increase in systemic vascular resistance caused by factors such as vessel disease or enhanced muscle tone in the vessel walls (vasoconstriction) may be the major cause of systemic hypertension.

It isn't definitive, but it's enough to clue in what the question wanted you to go for.

 

[boneill2]

My question is in reference to #112 on AAMC Test 8. THe question states: The most effective way to remove triethylamine during the workup of an organic reaction would be to extract the reaction mixture with aqueous:
A) sodium bicarbonate
B) sodium bisulfate
C) sodium sulfate
D) hydrochloric acid (correct answer)

The answer stated triethylamine will be soluble in an organic solvent however, I didn't think HCl was an organic solvent!? Can someone please shed some light on this question?

 

[trojanMD]

My question is in reference to #112 on AAMC Test 8. THe question states: The most effective way to remove triethylamine during the workup of an organic reaction would be to extract the reaction mixture with aqueous:
A) sodium bicarbonate
B) sodium bisulfate
C) sodium sulfate
D) hydrochloric acid (correct answer)

The answer stated triethylamine will be soluble in an organic solvent however, I didn't think HCl was an organic solvent!? Can someone please shed some light on this question?

Well i think the key thing to detect in this question was you wanted to extract a compound with an amine functional group. You should know that amines are only extracted by addition of HCl (as far as the MCAT goes). HCl will protonate the amine group, thus creating a positive charge on the molecule making it soluble.

I cant get to AAMC CBT 8 now so I dont know the context of the entire question but as far as I know, HCl is NOT an organic solvent. However, HCl will extract an amine from the organic layer. Perhaps you interpreted the answer wrong??

Hope this helps

 

[Kaustikos]

Well i think the key thing to detect in this question was you wanted to extract a compound with an amine functional group. You should know that amines are only extracted by addition of HCl (as far as the MCAT goes). HCl will protonate the amine group, thus creating a positive charge on the molecule making it soluble.

I cant get to AAMC CBT 8 now so I dont know the context of the entire question but as far as I know, HCl is NOT an organic solvent. However, HCl will extract an amine from the organic layer. Perhaps you interpreted the answer wrong??

Hope this helps

That's what it was. The extraction of the amine from an organic solution/workup. The wording of the question isn't exactly to die for.

 

[dreams]

anyone who took both # 7 adn #8 think that # 8 was much harder in Verbal (an the other sections as well)??

 

[tncekm]

anyone who took both # 7 adn #8 think that # 8 was much harder in Verbal (an the other sections as well)??

I've only taken 3,4,5,6,8, and I thought 8 was the hardest in the VR section for sure. I also thought it had some of the most ambiguous wording.

 

[fuzzywuz]

Question Regarding #103 (BS)

It asked what you will see on the H NMR for the aldehydic proton of 2-furaldehyde.

The response was a singlet. I thought it would be a singlet because I thought splitting would occur if there are chemically unequal H's 3 bonds away from the H that you are looking at. When I count 3 bonds I away, there was that lone hydrogen coming off the double bond on the right corner of the ring.

Any ideas?

EDIT:

Also question 134..wouldn't natural selection occur if there is less predation on the animal with the favorable trait, thus selecting them for survival and further reproduction..?

 

[Kaustikos]

Question Regarding #103 (BS)

It asked what you will see on the H NMR for the aldehydic proton of 2-furaldehyde.

The response was a singlet. I thought it would be a singlet because I thought splitting would occur if there are chemically unequal H's 3 bonds away from the H that you are looking at. When I count 3 bonds I away, there was that lone hydrogen coming off the double bond on the right corner of the ring.

Any ideas?

EDIT:

Also question 134..wouldn't natural selection occur if there is less predation on the animal with the favorable trait, thus selecting them for survival and further reproduction..?

The Hydrogen is 4 bonds away, or that's what I count.

For 134; that question is pretty much a discrete asking you about natural selection. Natural selection favors more offspring/higher success with generating offspring. Although it would seem logical to think that avoidance of predation would mean natural selection, the question is really asking you a question about what a characteristic of natural selection is.

 

[tncekm]

Exactly. The key to natural selection is 'survival of the fittest' and what that really means in the most true ecological sense is: survival of the organism who can reproduce most successfully.

If you took away a predator, that may allow another species that is more easily picked off by the same predator but competitively dominant for similar resources to outcompete said animal. So, less predation doesn't mean natural selection would favor that animal. Ecology is complex, but always remember that "producing offspring successfully = survival of the fittest = natural selection".

 

[CommSNTS]

Question on PS 42.

How can F- be the anion? I understand it is in the only soluble with Ag+ but the mixtures threw me off. Here's what I did:

In in the A + B mixtures, the compounds formed would be:

AgF + CaCr04 --> Ag2CrO4 + CaF

True that Ag2CrO4 is a white precipitate as the results mention, but CaF is a white precipitate which wasn't included.

Sorry if my wording doesn't make much sense.

 

[travelbug73]

Question on PS 42.

How can F- be the anion? I understand it is in the only soluble with Ag+ but the mixtures threw me off. Here's what I did:

In in the A + B mixtures, the compounds formed would be:

AgF + CaCr04 --> Ag2CrO4 + CaF

True that Ag2CrO4 is a white precipitate as the results mention, but CaF is a white precipitate which wasn't included.

Sorry if my wording doesn't make much sense.

All three solutions (A, B and C) are soluble in water. You know the cation is Ag+. Of the four anions that could be present, only AgF is soluble in water. The other three Ag2CrO4, AgCl and Ag2S form red, white and black precipitates respectively. Therefore, the anion in solution A must be F-

I don't understand what you mean by "CaF is a white precipitate which wasn't included." Are you asking how they differentiated between CaF2 and CaCl2?

If we did it per your method of mixing A and B, Ag2CrO4 would be a red precipitate and CaF a white precipitate. You can therefore conclude that the anion in solution A is F- because if it were Cl-, the resulting CaCl2 would be colorless and if it were S2-, the resulting CaS would be a black ppt (I think). This method would work only if they told you that they mixed A with B and then asked you what the original reactant was. In this particular question stem they only told you the cation was Ag+, no other information was given.

 

[ballofnerves]

anyone else have absolutely no idea what was going on the entire functionalism/behavioralism/cog sci passage???

awful.

Yeah the verbal was rough on this test. I normally score 10-12 on VR, but got a 9 on this one. I thought the test overall was more difficult than #4-7. I have been scoring 36 and 37 consistently on these, but got a 34 on #8.

 

[unsung]

#41. The ion responsible for the color of the solutions is:

A. sulfate, because sulfur has s and p orbitals.
B. nickel(II), because it has a charge of +2
C. nickel(II), because it has unfilled d orbitals
D. sulfate, because it is a resonance-stabilized anion

How are we supposed to know the color of a soln has anything to do with d orbitals ?

 

[unsung]

108. If restriction of blood flow to the kidnyes (by placing clamps on the renal arteries) resulted in an immediate but small increase in blood pressure, followed by the gradual development of severe hypertension, which hypothesis would these results best support?

A. Hypothesis A, because the clamps increased the vascular resistance to blood flow
B. Hypothesis A, because the clamps caused the kidneys to receive less blood
C. Hypothesis B, because the kidneys were responding to decreased glomerula blood pressure
D. Hypothesis B, because the volume of body fluids was probably decreasing

I answered A, but the answer is C. I understand why answer C makes sense-- low glomerular BP makes the kidneys reabsorb water & increase BP.

But A also made sense to me because the clamp restricts the blood vessel and increases resistance. So that should also increase blood pressure.

Why is A wrong?

 

[StarStup]

Question #130- the answer goes on to explain why E is the best answer and then at the end says that D is the best answer...I put D and am pretty sure it is D but the test marked it wrong...what is going on here? Am I misinterpreting what they are saying or is the answer messed up?

 

[dwc929]

no no. its saying " somebody incorrectly concluded that HCl was ionic. which of the following may have lead this person to believe that?"

its a crappily worded question. they are basically saying "which of the following describes an ionic compound." the only one that correclty describes something that is ionic is the that says "A 1M solution conducts electricity"

it took me like 5 min to figure out what the hell they were asking. its quesitons like these that make me despise the MCAT. just ask which of the following describes an ionic compound. jesus.

What makes answer choice B wrong? "a 1M solution freezes under 0C"

 

[Quantum Chem]

108. If restriction of blood flow to the kidnyes (by placing clamps on the renal arteries) resulted in an immediate but small increase in blood pressure, followed by the gradual development of severe hypertension, which hypothesis would these results best support?

A. Hypothesis A, because the clamps increased the vascular resistance to blood flow
B. Hypothesis A, because the clamps caused the kidneys to receive less blood
C. Hypothesis B, because the kidneys were responding to decreased glomerula blood pressure
D. Hypothesis B, because the volume of body fluids was probably decreasing

I answered A, but the answer is C. I understand why answer C makes sense-- low glomerular BP makes the kidneys reabsorb water & increase BP.

But A also made sense to me because the clamp restricts the blood vessel and increases resistance. So that should also increase blood pressure.

Why is A wrong?

In the text the first sentence in Hypothesis B's paragraph says that although increases in resistance to blood flow can quickly increase blood pressure the kidney should initiate some reflex to control the increase. So looking at the question we observe this initial increase, "an immediate but small increase in blood pressure", which can be explained by Hypothesis A, but "gradual development of severe hypertension" is not explained by A. So it seems that answer choice A only accounts for the initial increase and the long term increase isn't supported by A at all, but rather by Hypothesis B and the Kidney not doing this reflex to regulate the initial increase.

 

[Quantum Chem]

What makes answer choice B wrong? "a 1M solution freezes under 0C"

While ionic solutes will cause freezing point depression so can nonionic solutes. You can think of the square/rectangle conundrum as an analogy: "All squares are rectangles but not all rectangles are squares". Ionic compounds are substances that cause freezing point depression, but not all substances that cause freezing point depression are ionic. Also, the passage mentions nothing about freezing point depression but does say aqueous solutions of ionic compounds conduct electricity where those of covalent compounds do not. So the person in the question assumed that because HCl(aq) conducts electricity it must be ionic, but it isn't.

 

[Quantum Chem]

#41. The ion responsible for the color of the solutions is:

A. sulfate, because sulfur has s and p orbitals.
B. nickel(II), because it has a charge of +2
C. nickel(II), because it has unfilled d orbitals
D. sulfate, because it is a resonance-stabilized anion

How are we supposed to know the color of a soln has anything to do with d orbitals ?

You just do. If you did redox reactions in a chem lab then you might be able to remember the color of a solution changing when adding some oxidizing agent. Same principle, an ion gained/lost electrons changing its properties so that are visually noticeable. You might have also done it in an organic lab where you made some sort of aromatic compound even more conjugated and the end product was a different color. Both of these examples are all about those electrons and where they are at.

 

[Adnama]

I don't mean to post this twice - but I did not see there was a section just for this test.

Anyways, can someone explain the reasoning behind #27.

Thank you.

 

[fmaemc2]

I thought verbal on this was mad hard.. I have been getting 10s and 11s and came out with a 7 just now. Quite disheartening considering I'm taking the MCAT this upcoming friday.

Physical and Biological were OK, but there were some really poorly worded questions that through me off.

Anyone else think verbal was nuts?

 

[Revilla]

I'm having trouble with number 103. I know you guys talked about it above, but I'm still confused. Which proton are we looking at here? I was looking at the carbonyl carbon and the lone hydrogen coming off it.

 

[Revilla]

I'm having trouble with number 103. I know you guys talked about it above, but I'm still confused. Which proton are we looking at here? I was looking at the carbonyl carbon and the lone hydrogen coming off it.

Never mind. I looked up my old Orgo notes from class. I forgot you have to look at the adjacent carbon, not the carbon it's asking about.

 

[coldviva204]

Hi, can anyone help me with a question? I am confused about #50: When sound reflect off a surface, I know that speed of sound remained unchanged before and after the reflection. But I also thought frequency doesn't change either, or am I wrong?

 

[minhaj]

coldviva, I am going to try to explain it the way I thought through it. I might wrong, if that is the case someone please correct me. Here it goes:

Since we know that E=hf, and as the light bounces off of the imperfect reflector, some of the energy goes through into another medium the rest of it reflects back. This change in energy of the wave/amplitude would also affect the frequency of the wave as indicated by the E=hf equation.

 

[coldviva204]

Thanks upstairs, that makes more sense. I didn't not take the "imperfect reflector" into account.

 

[1Cor1557]

I do not understand what the qualitative factors of q = q(and some subscript) represent. AAMC explanation seems to mean entering light and exiting, but that is still my guess. Any help is appreciated!

 

[Tiss229]

Can anyone explain #38 on the PS to me?

If red litmus paper is dipped into the Na2CO3 solution, it will:
A) remain red, because carbonate is an acidic salt.
B) remain red, because sodium carbonate is neutral.
C) turn blue, because carbonate reacts with water to produce OH–.

In water, carbonate will undergo the following reaction: CO32–(aq) + H2O(l) ® HCO3–(aq) + OH–(aq). Red litmus paper will turn blue in a base. Thus, C is the best answer.

D) turn blue, because sodium ions form sodium hydroxide in water.

I picked D... why is this not the case?

 

[engineeredout]

I just finished taking this.

10PS/11VR/10BS - 31. On par with my other exams.

I really thought I tanked the PS. Was it me or was the PS really ****ing hard? PS is usually my strong subject.

I still did WAY better than I thought I did. Guess it just goes to show you its hard to predict your score coming out of an exam (and why voiding is a terrible idea).

 

[engineeredout]

Question #7 (CBT): A nucleus can emit a photon??