AAMC CBT5 and 5R OFFICIAL Q&A

For Biological Science section (18th question, Item # --> ?):

How do we know that the macronuclei do not participate in mating so only the genotypes of the micronuclei need to be considered?

also in passage IV... I know a carboxylic salt needs to be acidified to become an anhydride, but how are we suppose to know that it also requires heat?

Is it because the forward reaction is favorable, therefore the reverse would be nonspontaneous? And nonspontaneous reactions are endergonic and require a positive enthalpy?

because its a dehydration, there is a loss of water, anytime you have a loss of water its favored to occur under the addition of heat

okay, seriously....just did aamc 5r verbal......from question 78-109, i only missed 5 questions...then, the bomb hit me...questions 110-127, i missed 12 questions...really, i missed 8 on that damn picasso passage alone, and i did not understand a thing i was reading about candolins??and butch or watever it was...about boats and paris..

What are your usual results? It could be that you ran out of stamina.

SN2ed said:

What are your usual results? It could be that you ran out of stamina.

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i got a6, then a 7 on 4r verbal. and a 9 on this one. maybe im improving? but, maybe you are right, perhaps i did run out of stamina...not sure, but i started to get my answers correct again towards the end.

Well, since you haven't taken many tests, I'd keep going and see if there's a trend. It could be that those couple of passages were genuinely tough for you. Go back over those passages and try to see what happened.

Physical sciences question #14

According to Equation 1, the concentration of the polymer with respect to [HPO42–] is:
A) n[HPO42–].
B) n2[HPO42–].
C) (1/n)[HPO42–].
D) (1/n2)[HPO42–].
According to the balanced coefficients in Equation 1, each time one molecule of the polymer (CP)n is formed, there also are n hydrogen phosphate ions HPO4-2 produced. Thus, the concentration of (CP)n must be 1/n times the concentration of the HPO4-2. The correct response is C.
I just don't understand the correlation at all with respect to the n. Someone? Anyone?

Maybe this example will help.

Ca(OH)2 <----> Ca2+ + 2OH-

For every 2 moles of OH- there is 1 mole of Ca2+. Therefore, for every 1 mole of OH- there are 1/2 moles of Ca2+.

Now just replace the coefficient of OH- (2) with n and you get your answer: ratio = 1/n : 1

Kaustikos said:

Physical sciences question #14

According to Equation 1, the concentration of the polymer with respect to [HPO42–] is:
A) n[HPO42–].
B) n2[HPO42–].
C) (1/n)[HPO42–].
D) (1/n2)[HPO42–].
According to the balanced coefficients in Equation 1, each time one molecule of the polymer (CP)n is formed, there also are n hydrogen phosphate ions HPO4-2 produced. Thus, the concentration of (CP)n must be 1/n times the concentration of the HPO4-2. The correct response is C.
I just don't understand the correlation at all with respect to the n. Someone? Anyone?

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the passage never balanced the equation, so "n" just represents any integer.

its asking about the relationship between the polymer (CP) and HPO42-. the equation says for every mole of CP you have n mol of HPO42-.

you can just plug in numbers for n...in this case i will use the number 3. if you have 3 moles of HPO42- that means you will have 1 mole of CP. in other words, for every 1 mole of CP you will have 1/3 (1/n) amount of HPO42-.

did tha tmake sense? its kind hard communicate over SDN

I got a 32 as well (11/10/11). It was my lowest score so far, but I mean, come on, a 32 is great to be the "lowest." It did feel harder than #3 (got a 36 on that one).

So this maybe a stupid question but #36 for bio how does longevity not correlate with relatively long life span? Is it b/c the choice says "individuals" and it is referring to longevity of the species??

TypeSH07 said:

So this maybe a stupid question but #36 for bio how does longevity not correlate with relatively long life span? Is it b/c the choice says "individuals" and it is referring to longevity of the species??

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Yea pretty much. Long life span means the long life of an individual, while longevity is the length of existence of a species.

So I just wanted to make sure that my thought process for this wasn't wrong. For #7 on PS I didn't really do much math. Since 2M is 2 mol/L and it's a 1:1 ratio of Na2CO3 to CO2 I just said found that .5 mols would be 1/4 of a liter(250ml). Is this a logical thing to do or did I just get lucky with the numbers for this specific problem?

That's basically it. Since you need 11.2 L of CO2, you must need 0.5 moles of CO2. 1:1 ration means you need 0.5 moles of Na2CO3.

(0.5 moles)/(2 moles/L) = 0.25 L = 250 mL

Chemist0157 said:

That's basically it. Since you need 11.2 L of CO2, you must need 0.5 moles of CO2. 1:1 ration means you need 0.5 moles of Na2CO3.

(0.5 moles)/(2 moles/L) = 0.25 L = 250 mL

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Cool thanks. Could you explain #24 by any chance??

I also sent you a PM about something..

I saw and replied.

CO2 - impossible since there is no carbon
O3 - would have required that copper metal be reduced and we "never" see that (since oxygen got oxidized)

These two are ruled out pretty easily, but we still have NO and H2.

It really seems to me that background knowledge is needed here; the AAMC explanation says both are plausible but H2 is not observed (whoopie, thanks for the "explanation") but NO is because N is more easily reduced from HNO3 to NO than H is from HNO3 to H2.

Maybe someone else can help; I didn't really think of it that way, and the AAMC explanation is lacking.

#46 - "Diffuse"

what exactly does that mean?


This is PS

thanks

The spreading of light from a source.

Since a laser is coherent light (all photons travel in the same direction), the light cannot diffuse (diverge). "Diffuse" may not be the best word...

BloodySurgeon said:

For Biological Science section (18th question, Item # --> ?):

How do we know that the macronuclei do not participate in mating so only the genotypes of the micronuclei need to be considered?

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I got the right answer...but now i think i was lucky! That whole passage sucked, but I still managed to do well
Since the macronuclei are homozygous recessive, the progeny will also be homozygous recessive for the macronuclei. So, we don't take that into consideration when determining the percent of progeny that are homozygous for both traits.
That was my reasoning...but reading their explanation, I think I'm wrong. Something about how the macronuclei divide must be the reason.

BloodySurgeon said:

also in passage IV... I know a carboxylic salt needs to be acidified to become an anhydride, but how are we suppose to know that it also requires heat?

Is it because the forward reaction is favorable, therefore the reverse would be nonspontaneous? And nonspontaneous reactions are endergonic and require a positive enthalpy?

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Anhydrides are really unstable and carboxylates are really stable. So, you NEED heat for that reaction to work.

Chemist0157 said:

I saw and replied.

CO2 - impossible since there is no carbon
O3 - would have required that copper metal be reduced and we "never" see that (since oxygen got oxidized)

These two are ruled out pretty easily, but we still have NO and H2.

It really seems to me that background knowledge is needed here; the AAMC explanation says both are plausible but H2 is not observed (whoopie, thanks for the "explanation") but NO is because N is more easily reduced from HNO3 to NO than H is from HNO3 to H2.

Maybe someone else can help; I didn't really think of it that way, and the AAMC explanation is lacking.

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If H2 were to form, it would have occurred in the water as well. hard question, though.

BloodySurgeon said:

For Biological Science section (18th question, Item # --> ?):

How do we know that the macronuclei do not participate in mating so only the genotypes of the micronuclei need to be considered?

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If I remember correctly, the diagram/history showed that the macronuclie actually degenerate and are not conserved in the mitosis and THAT is why we do not concern ourselves with the initial macronuclei.

And I agree, that passage really sucked. 3 of those questions annoyed me and I, for the first time in a biology section, skipped it.

PS #42 - it says "from ground level".. isn't this a misprint??

BS 142:
II. in vitro cultivation of probable pathogen was difficult.
I took this to mean that it couldn't be cultivated in vitro. but i guess I have to take the wording very literally, ie. "it was difficult to cultivate in vitro, but it could still be done" ???? in which case it would be incorrect since they are obligate parasites?? so nitpicky!

also,

PS 43:
if the height is reduced by a half, then v = sqrt2g(h/2) ....this equals to a v that is slowed by sqrt2? do i just suck at math and not see what is obvious?

Archdelux said:

PS #42 - it says "from ground level".. isn't this a misprint??

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yeah this kinda threw me off too. but i didnt see any other way to solve it so i just assumed they meant from A.

happygirl said:

BS 142:
II. in vitro cultivation of probable pathogen was difficult.
I took this to mean that it couldn't be cultivated in vitro. but i guess I have to take the wording very literally, ie. "it was difficult to cultivate in vitro, but it could still be done" ???? in which case it would be incorrect since they are obligate parasites?? so nitpicky!

also,

PS 43:
if the height is reduced by a half, then v = sqrt2g(h/2) ....this equals to a v that is slowed by sqrt2? do i just suck at math and not see what is obvious?

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For 43: it's asking relative to the v at a position higher.
V1^2/V2^2 = g10/g20. From that, you see that the velocity is slower by a factor of (2)^(1/2)

That passage about the micro/macronucleii SUCKED. I could sit here and read it 2 more times and it still wouldn't make sense.... sigh. Ironically, I did okay on BS but tanked the verbal. So bizarre.

From rxns 3-5, what can be determined about the relative concentrations of CFCs and O2?

Answer: A catalytic amount of CFC can produce much O2.

I'm completely clueless on this one. If you write out the net rxn for rxns 3-5, you get F3CCl + O3 + O --> F3C' + Cl' + O2 (where ' indicates radical)

so why is it a "catalytic amount"?? I guessed it was 1 equivalent of CFC to produce 2 equivalents of O2.

Can someone explain this to me?? I'm getting way frustrated trying to figure this out

Thanks!!

mytoechondriac said:

From rxns 3-5, what can be determined about the relative concentrations of CFCs and O2?

Answer: A catalytic amount of CFC can produce much O2.

I'm completely clueless on this one. If you write out the net rxn for rxns 3-5, you get F3CCl + O3 + O --> F3C' + Cl' + O2 (where ' indicates radical)

so why is it a "catalytic amount"?? I guessed it was 1 equivalent of CFC to produce 2 equivalents of O2.

Can someone explain this to me?? I'm getting way frustrated trying to figure this out

Thanks!!

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Catalysts are used/reformed. I believe in that question, Cl and ClO do both that. I don't know why your answer was wrong though b/c it's what I answered as well.

Don't really have a question yet, just finished the exam and got 11PS 10VR 10 BS so I'm happy

#41: When a strip of Cu is placed in a solution of HNO3 a gas evolves? Which is it?
A) NO
B) CO2
C)H2
D)O3

I know the answer is NO. I thought it was H2. What is the logic behind this answer?

Hi! Okay, so I know I'm missing something really obvious right now, but for number 39, isn't the mass of the person + the toboggan = 60 kg, so the force would be mg= 60*g Newtons? I know this is a simple problem, but I idiotically can't seem to understand why the answer is 60N(l) and not 60kg*g*l. Can someone please enlighten me? Thanks so much!

pk1213 said:

Hi! Okay, so I know I'm missing something really obvious right now, but for number 39, isn't the mass of the person + the toboggan = 60 kg, so the force would be mg= 60*g Newtons? I know this is a simple problem, but I idiotically can't seem to understand why the answer is 60N(l) and not 60kg*g*l. Can someone please enlighten me? Thanks so much!

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It says in the problem

The toboggan and the rider are opposed by a 60N constant force

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Since you're looking for the energy lost to friction, all you need to take into consideration is the 60N frictional force.

Wow, I knew I was going to kick myself when someone explained it to me! I completely missed the 60 N friction force value given in the passage...Oh dear. Thanks so much!

pk1213 said:

Wow, I knew I was going to kick myself when someone explained it to me! I completely missed the 60 N friction force value given in the passage...Oh dear. Thanks so much!

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haha. i just did the PS section today. EXACT same thing happend to me. I can't believe i read over that. Sigh, careless errors will be the end of me. I got a 12 (highest PS score ever!) though, so im a happy camper.

Yes Sir said:

#41: When a strip of Cu is placed in a solution of HNO3 a gas evolves? Which is it?
A) NO
B) CO2
C)H2
D)O3

I know the answer is NO. I thought it was H2. What is the logic behind this answer?

Click to expand...

I also put H2 for this question. The nitric acid dissociates into H+ and (NO3)- ions in solution right? Looking at that and not having any info on the reduction potential of (NO3)-, I figured H+ would get the electrons and be reduced to form H2(g). I mean, it is a positive ion that would like to become neutral no? How exactly does the N atom being more electronegative than H really matter when the whole complex is (NO3)-? Reducing (NO3)- to produce NO(g) just didn't cross my mind as being plausible.

So, are insects representative of all arthropods?

Item 131

After observing the well-defined nervous system of several insect species, a student concludes that all arthropods must have a true coelom. Is such a conclusion warranted?
A) No; insects are not representative of all arthropods.
B) No; coelom development and nerve tissue development are independent processes.

unsung said:

That passage about the micro/macronucleii SUCKED. I could sit here and read it 2 more times and it still wouldn't make sense.... sigh. Ironically, I did okay on BS but tanked the verbal. So bizarre.

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x2!!! that is probably the toughest bio passage ive seen. i just stared at it and cried a little on the inside when i first saw it. it just looks so damn intimidating.... i went over the answers...i still dont get it. o well.

Yes Sir said:

#41: When a strip of Cu is placed in a solution of HNO3 a gas evolves? Which is it?
A) NO
B) CO2
C)H2
D)O3

I know the answer is NO. I thought it was H2. What is the logic behind this answer?

Click to expand...

Yeah this question sucks how am giving a chart would make this question acceptable considering most transition metal have a negative reduction potiential and H gas is zero.

Also did anyone miss the one about the speed of the ocean wave because the question was ambiguous.

If ocean waves strike the shore every 3.0 s and the horizontal distance between adjacent crests and troughs is 1.0 m, what is the average speed of the waves?

This could mean either the distance between adjacent troughs (one wavelenth) is 1m (like I thought it meant) or it could mean 0.5 wavelength. Why can't they just make it clear by says "the distance between AN adjacent peak and trough is 1m". I feel like they do a ****ty job with ambiguity.

Phys Sciences (CBT Question 6)
From rxns 3-5, what can be determined about the relative concentrations of CFCs and O2?
Answer: (C) A catalytic amount of CFC can produce much O2.

This question has been posted earlier as well. I understand that the Cl radical is not consumed in the reaction and is reformed, similarly for the ClO radical.

What I don't understand: the CFC in the passage is defined as CF3Cl. When I read this question, I assumed that CF3Cl got "altered" in the reaction - because it was broken down into a CF3 radical and Cl radical. Since catalysts are not altered or consumed in a reaction, I assumed this choice (C) could not be correct.

The answer I picked was (B) - 1 equivalent of CFC is required to produce 2 equivalents of O2. Can someone explain why this is wrong?
** I eliminated A and D so had I known this was wrong, I would have picked C.

Thanks! Anyone who understood this question please reply!!!!!!!!

Also did anyone miss the one about the speed of the ocean wave because the question was ambiguous.

If ocean waves strike the shore every 3.0 s and the horizontal distance between adjacent crests and troughs is 1.0 m, what is the average speed of the waves?

This could mean either the distance between adjacent troughs (one wavelenth) is 1m (like I thought it meant) or it could mean 0.5 wavelength. Why can't they just make it clear by says "the distance between AN adjacent peak and trough is 1m". I feel like they do a ****ty job with ambiguity.

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I got this one correct, but I do see what you mean in that it is somewhat ambiguous. I think they should have said the distance between AN adjacent crest and trough = 1m.

Quote:
Originally Posted by Yes Sir
#41: When a strip of Cu is placed in a solution of HNO3 a gas evolves? Which is it?
A) NO
B) CO2
C)H2
D)O3

I know the answer is NO. I thought it was H2. What is the logic behind this answer?

I also put H2 for this question. The nitric acid dissociates into H+ and (NO3)- ions in solution right? Looking at that and not having any info on the reduction potential of (NO3)-, I figured H+ would get the electrons and be reduced to form H2(g). I mean, it is a positive ion that would like to become neutral no? How exactly does the N atom being more electronegative than H really matter when the whole complex is (NO3)-? Reducing (NO3)- to produce NO(g) just didn't cross my mind as being plausible.

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I put H2 also.

Cu + HNO3(aq) -----> Cu(NO3)2 + H2 [WRONG]
Cu + HNO3 (aq) ----> CuO2 + NO

I guess what they are saying kind of makes sense - Cu gets oxidized in both equations above but it is more likely for N to be reduced (it being more EN), than H to be reduced.

But, I thought along the same lines of you Matt. The first (wrong) equation that I thought was happening seems more logical, and formation of H2 (g) I thought would be stable / a good thing.

When you see such a problem how should one approach determining correct products?

So, are insects representative of all arthropods?

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Yeah I picked "A" too. I don't understand why this is wrong, because of the use of the word ALL in the answer choice. Insects are NOT representative of ALL arthropods because there ARE arthropods that are not insects right? And so that choice could be a plausible answer to the question. Help?

BS Item 131
After observing the well-defined nervous system of several insect species, a student concludes that all arthropods must have a true coelom. Is such a conclusion warranted?
A) No; insects are not representative of all arthropods.
B) No; coelom development and nerve tissue development are independent processes.

JoeGator86 said:

Also did anyone miss the one about the speed of the ocean wave because the question was ambiguous.

If ocean waves strike the shore every 3.0 s and the horizontal distance between adjacent crests and troughs is 1.0 m, what is the average speed of the waves?

This could mean either the distance between adjacent troughs (one wavelenth) is 1m (like I thought it meant) or it could mean 0.5 wavelength. Why can't they just make it clear by says "the distance between AN adjacent peak and trough is 1m". I feel like they do a ****ty job with ambiguity.

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I agree. I missed this question too. The way they said it, it seems that they're saying "the space between adjacent crests and [adjacent] troughs is 1.0m," but they meant "the space between adjacent (crests and troughs) is 1.0 m."

On BS 104: It asked what the best way to counteract the effects of Drug Y (noncompetitive inhibitor of Ach receptor) was. I put administer a competitive receptor stimulator, thinking that it meant competitive with Drug Y, so it would normally be considered a allosteric activator of ACh receptor. Is that right, or did the test mean competitive receptor stimulator that competes with Ach (not drug Y) but still stimulates the receptor?

I did worse on this one than all my previous AAMCs and the test is on Friday!

Appologies in advance for this question, but I know I am missing something:

I thought transparent meant that it allowed light to pass through. The question stem says the best scintillators are nearly transparent to the wavelengths of light that they emit. The answer makes sense, but how could I have figured this out based on the passage information?

Thanks in advance!