Group Study Thread and Other Micellaneous Posts

[SDN]

This thread is for students to ask and answer each other's questions for the MCAT, DAT, OAT, and PCAT subjects. All posts from the other Q & A threads that are not either students' questions or moderators' replies will be moved to this thread. Students, please post your own answers to other students' questions here in this thread--or else in the main MCAT forum--rather than in the regular Q & A threads.

If you are a pre-health (MCAT, PCAT, DAT, OAT) test prep instructor, or you have a graduate-level background in one of the MCAT subjects, or you are a senior undergrad who scored well on the MCAT, and you would like to help answer questions for one of the regular Q & A threads, please PM Shrike or QofQuimica and let them know. Again, all undergrad students who are currently studying for any of these tests should NOT post answers to other students' questions in any of the regular Q & A threads. Thanks to everyone for your cooperation..

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[captaintripps]

One more question guys, this one about circulation and the MCAT. In tracing the blood around the heart and to the lungs I found Kaplan's explanation to be well...krappy. The left side I think pumps the deoxygenated blood, I know there's a systole and a diastole which are the lub/dub. Blood from the lower body is from the inferior vena cava, upper superior. But I'm just having trouble piecing it all. Can someone give me a good rundown for the MCAT?

Vena cava: deoxy blood > right atrium > atrioventricular tricuspid valve > right ventricle > pulmonic valve/artery > pulmonary circuit > pulmonary vein (oxygenated blood) > left atrium > atrioventricular mitral valve > left ventricle > aortic valve > aorta to systemic circulation.

So then - the left side does not pump deoxygenated blood, just the opposite. Systole is ventricular contraction (pumping) and diastole is ventricular relaxation (filling). Check out a physiology textbook to get familiar with this as well as the electrical properties of the heart i.e., SA node AV node...

 

[Neurolemma]

So then - the left side does not pump deoxygenated blood, just the opposite.

Yeah, thats what I would think too. The aorta is actually the largest artery. When the left ventricle contracts, it really contracts, meaning the pressure is enormous. And this is also why the left ventricle contains more cardiac muscle than the right. Of course the pressure decreases as the blood moves along. You may want to remember the relative sizes of the blood vessels as well. From largest diameter to smallest:

Artery ---> arteriole ---> capillary ---> venule ---> vein

 

[Neurolemma]

I should've said, the pressure in the aorta is enormous. Excuse me. If I remember right, the aorta itself contracts rather passively. Which is why the walls of the aorta (and all other arteries) differ considerably, relative to tissue structure, from the other types of blood vessels (the pressure is greater in the arteries). Which implies that the proportion of intima, elastica, & adventitia differs, from blood vessel to blood vessel. I don't recall the exact proportions, unfortunately, but I think tunica elastica is greater in the aorta? Elastica = elastic = recoil.

 

[Nitya2284]

I should've said, the pressure in the aorta is enormous. Excuse me. If I remember right, the aorta itself contracts rather passively. Which is why the walls of the aorta (and all other arteries) differ considerably, relative to tissue structure, from the other types of blood vessels (the pressure is greater in the arteries). Which implies that the proportion of intima, elastica, & adventitia differs, from blood vessel to blood vessel. I don't recall the exact proportions, unfortunately, but I think tunica elastica is greater in the aorta? Elastica = elastic = recoil.

Do we have to know about the tunica elastica?

 

[RAD11]

I was reading my Examcrackers materials and I'm confused on 2 questions:

1) Compared to an electron with a principal quantum number of 1, an electron with a principal quantum number of 2 will have:

a. a lower energy
b. a higher energy
c. a negative spin
d. a positive spin

I picked b. because I thought that the further the electrons from the nucleus, the higher the energy. But their answer is a. Their explanation in the back of the book is: The principal quantum number represents the energy level of the electron. The lowest energy shell is n=1. As n increases, the shells move farther from the nucleus and energy increases. So wasn't I right? Do you think this was a typo?

2) Which of the following best explains why sulfur can make more bonds than oxygen?

a. Sulfur is more electronegative than oxygen.
b. Oxygen is more electronegative than sulfur.
c. Sulfur has 3d orbitals not available to oxygen.
d. Sulfur has fewer valence electrons.

I got this question right by process of elimination, but I'm trying to understand why choice c. is the correct answer. I thought that since sulfur is in group VIA that it has 3p orbitals and that the transition elements are the only ones with d orbitals. Can you please explain why choice c. is the correct answer? The explanation in the back of the book is not clear to me. They explain that because sulfur is larger than oxygen, sulfur has 3d subshells available that allow electrons to form bonds and break the octet rule of Lewis structure.

Thanks for you help!

 

[frany584]

Rad11, I just saw ur question and wanted to let you know that it was a typo. I love Examkrackers, but their books do have a bit of typos. In case you are unsure about other questions u can go to the website, and look under the forums. Thats where i found out if the questions were typos or not.

 

[RAD11]

Rad11, I just saw ur question and wanted to let you know that it was a typo. I love Examkrackers, but their books do have a bit of typos. In case you are unsure about other questions u can go to the website, and look under the forums. Thats where i found out if the questions were typos or not.

Hey frany584, thanks a lot for clarifying that for me. I was sure I had the right answer, but you never know. I still need the explanation to question # 2, though

 

[frany584]

Hey RAD11, there is another discussion about d orbitals and why certain atoms can/cannot have five bonds on the first page of this thread, i hope it provides some clarification:

Posted by Learfan:

1. I think that you are confusing hybridization of atoms that are bonding to other atoms with electron configurations for lone atoms. All atoms have d-orbitals, but elements that are in row 3 or greater of the periodic table have low-lying d-orbitals that are available for bonding. A phosphorus central atom with five bonds WOULD have one of its 3d orbitals included in its hybridization. In other words, when it has five bonds and trigonal bipyramidal geometry, its hybridization is sp3d. That d comes from one of the 3d orbitals in the phosphorus atom. So there are five sp3d orbitals, used to make the five bonds to the phosphorus. Keep in mind that elements in rows 1 and 2 will NEVER exceed their octets, because aren't any 1d or 2d orbitals to make sp3d or sp3d2 hybrid orbitals. So nitrogen, right above phosphorus, can never have five bonds.

 

[QofQuimica]

Do we have to know about the tunica elastica?

no. You can save it for medical school.

 

[Neurolemma]

Okay, looks like I gave some wrong info. I studied this last yr... so pardon moi. There is indeed a tunica elastica, but it has nothing to do with blood vessel pressure. These are the three layers: tunica intima (think intimate - inside - innermost), tunica media (think middle), & adventitia (think outermost, in this case, connective tissue).

According to http://www.maexamhelp.com/id99.htm:

"Blood is pumped from the ventricles into large elastic arteries that branch repeatedly into smaller and smaller arteries until the branching results in microscopic arteries called arterioles. The arterioles play a key role in regulating the blood flow into the tissue capillaries. About 10% of the total blood volume is in the systemic arterial system at any given time."

Example: blood is pumped from the left ventricle to the aorta (which is an elastic artery). Remember that the left ventricle has to pump blood to the entire body; hence the great pressure in the aorta. The walls of the aorta will expand (contract) as a result; they need to be able to both contract (without rupturing) and recoil. The expansion and recoil is made possible by the elastic tissue of the tunica media. The adventita prevents the vessel from rupturing.

According to

http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab12b/EXAMPLES/Exmusart.htm:

"In muscular arteries such as the one shown at left, the wall is composed mainly of smooth muscle. Elastic CT is present, to be sure, but not nearly to the extent that it is in the elastic arteries.
The smooth muscle of the wall of distributing arteries makes them very extensible, and also provides for a counter force to be exerted. As the vessel expands the smooth muscle cells are stretched. Reacting to this they begin to contract. The peak of their contraction comes at about the point where systole ends and diastole begins; thus the contraction of the arterial walls dampens out the pulsations of the flow to provide a more or less steady supply of blood at normal pressure into the capillary beds."

This makes sense if you consider that muscular arteries are also the distributing arteries. If they simply pumped blood at full speed into capillaries, the capillaries (which are extremely thin and function as diffusion mechanisms - think " pulmonary alveoli" here) - would rupture. Smooth muscle contracts slowly; this allows the blood to flow into capillaries at exactly the right rate. As for capillaries, their walls consist of a simple layer of endothelium (simple squamous eptithelium). This makes sense if you consider that the red blood cells (erythrocytes) of the capillary which passes through a tissue must somehow release the oxygen they contain, and pick up CO2. This is accomplished via diffusion. Venules connect capillaries to veins; veins carry deoxygenated blood back to the right side of the heart. Veins also contain valves, to prevent the backflow of blood. The pressure in veins is low, hence the valves.

 

[Nitya2284]

Yeah, thats what I would think too. The aorta is actually the largest artery. When the left ventricle contracts, it really contracts, meaning the pressure is enormous. And this is also why the left ventricle contains more cardiac muscle than the right. Of course the pressure decreases as the blood moves along. You may want to remember the relative sizes of the blood vessels as well. From largest diameter to smallest:

Artery ---> arteriole ---> capillary ---> venule ---> vein

Circulation goes like this : left heart --> aorta --> arteries --> arterioles ---> capillaries ---> venules --> veins --> vena cava --> right heart.

THe maximum pressure is in aorta and the lowest is in the vena cava, i think

 

[Neurolemma]

Circulation goes like this : left heart --> aorta --> arteries --> arterioles ---> capillaries ---> venules --> veins --> vena cava --> right heart.

THe maximum pressure is in aorta and the lowest is in the vena cava, i think

You are mostly correct. Its already been mentioned in this thread... deoxygenated blood enters the right side of the heart (superiorly, from the superior vena cava, inferiorly, from the inferior vena cava, while the left side of the heart pumps oxygenated blood to the rest of the body. I think its also good to know that blood flows from the right side of the heart to the lungs before going to the left side. I don't know if the MCAT will question you about semilunar valves/mitral valves & all that. Also remember that the aorta is itself an artery (the largest one, in fact). So to somewhat modify what you wrote above:

Right atrium ---> Right ventricle ---> Pulmonary trunk ---> Pulmonary arteries (lungs) ---> Pulmonary capillaries ---> Pulmonary veins ---> Left atrium ---> Left ventricle ---> aorta (elastic artery) ---> muscular arteries ---> arteriolies ---> capillaries ---> venules ---> veins ---> vena cavae

Just remember that between "right" and "left" comes pulmonary, and that pulmonary refers to lungs; the rest will come easily. Another point the MCAT might test you on is the difference between systemic & pulmonary circulation. Systemic (think system, think body) = circulation to the rest of the body, pulmonary = circulation to the lungs. The two are not exactly independant of each other, which is why I like to remember it in one go. There is also coronary circulation, which just means there are two coronary arteries (right main & left main) which give blood to the tissues of the heart.

The maximum pressure is in the aorta, and the lowest is in the right atrium. If you want to be more exact:

"As blood leaves the aorta and flows through the systemic circulation, its pressure falls progressively as the distance from the left ventricle increases. Blood pressure decreases to about 35mmHg as blood passes from systemic arteries to systemic arterioles and into capilliaries. At the venous end of capilliaries, blood pressure has droped to about 16mmHg. Blood pressure continues to drop as blood enters systemic venules and then veins because these vessels are farthest from the left ventricle. Finally, blood pressure reaches 0mmHg as blood flows into the right ventricle."

 

[Nitya2284]

I was wondering if Shrike's method for attacking PS passages applies to Bio-- is it a good to skim the passage at most and focus on the reactions, figures, graphs, equations, etc then dig into the questions? I could see where certain subjects (CAC, maybe certain physio passages) this would be great, but what about genetics passages? Any thoughts?

Aside to Shrike: I used your method for PS, and went from 9's and 10's to 12's on my practice exams. Thanks for making my toughest section my strongest!

What was the method that you used that made you go up so many points, will u please let me know?? physics is my weak subject too

 

[scooter31]

Look here, post 7

 

[RAD11]

From Examcrackers 1001 Questions in MCAT Chemistry:

In the following reaction, which is run at 600K, 4.5 moles of nitrogen gas are mixed with 11 moles of hydrogen gas:

N2(g) + 3H2(g) --> 2NH3(g)

The reaction produces 6 moles of ammonia. What is the percent yield of ammonia?

A. 42%
B. 57%
C. 82% --> ANSWER
D. 100%

Their explanation in the back of the book: Hydrogen is the limiting reagent. Eleven moles of hydrogen should produce 11 x 2/3 = 7.3 moles of ammonia. If it actually produces 6 moles, the yield is 6/7.3, which is a lot more than half.....WHAT???!!!!! Can someone please explain this to me? How did hydrogen become the limiting reagent?


Does the question always have to give you the starting amount in moles or grams in order to figure out the limiting reagent and/or the percent yield?

Thanks a bunch!

 

[philchemist]

From Examcrackers 1001 Questions in MCAT Chemistry:

In the following reaction, which is run at 600K, 4.5 moles of nitrogen gas are mixed with 11 moles of hydrogen gas:

N2(g) + 3H2(g) --> 2NH3(g)

The reaction produces 6 moles of ammonia. What is the percent yield of ammonia?

A. 42%
B. 57%
C. 82% --> ANSWER
D. 100%

Their explanation in the back of the book: Hydrogen is the limiting reagent. Eleven moles of hydrogen should produce 11 x 2/3 = 7.3 moles of ammonia. If it actually produces 6 moles, the yield is 6/7.3, which is a lot more than half.....WHAT???!!!!! Can someone please explain this to me? How did hydrogen become the limiting reagent?


Does the question always have to give you the starting amount in moles or grams in order to figure out the limiting reagent and/or the percent yield?

Thanks a bunch!

Hydrogen is the limiting reagent because in the example if you have 4.5 moles of nitrogen equals 13.5 moles of hydrogen (the ratio of nitrogen to hydrogen is 1:3). In the question stem they tell you that you use 11 moles of hydrogen, which is less than the 13.5 moles calculated above. This makes hydrogen the limiting reagent because the reaction is limited by the actual amount (11 moles) of hydrogen used. Since hydrogen is the limiting reagent you can use the ratio of hydrogen to ammonia (3:2) to figure out the number of moles of ammonia produced. 11/x=3/2 or x=(2/3) 11=7.3. Since you can't use a calculator during the mcat, you know that 6/7.3 is much greater than 50% so you can eliminate choices a and b, and d doesn't make sense because we know that the actual yeild(6) doesn't equal the theoretical(7.3). So the answer is c. I hope this helps. And more importantly I hope I'm right.

 

[frany584]

RAD11, i do the problem just a tad different than philchemist, but get the same answer and thought maybe seeing a different approach might help as well . I do it by converting the moles of reactants given, to moles of product:

4.5 moles N2 (2 moles NH3/ 1 mole N2) = 9 moles NH3
11 moles H2 (2 moles NH3/ 3 moles H2) = ~7.3 moles NH3

looking at that i can see that the amount of hydrogen given produces less product, thus it has to be the limiting reagant. Because hydrogen is the limiting reagent, it determines the maximum amount of product that can be produced (our theoretical yield). Now, my actual yield = 6 moles. So the percent yield = actual/theoretical *100. hope that helps!

 

[izibo]

For a second, I thought the subject was orgasmal biology... so dissapointed.

 

[scooter31]

For a second, I thought the subject was orgasmal biology... so dissapointed.

Check the urology forum, they may have something up your alley

 

[QofQuimica]

Hydrogen is the limiting reagent because in the example if you have 4.5 moles of nitrogen equals 13.5 moles of hydrogen (the ratio of nitrogen to hydrogen is 1:3). In the question stem they tell you that you use 11 moles of hydrogen, which is less than the 13.5 moles calculated above. This makes hydrogen the limiting reagent because the reaction is limited by the actual amount (11 moles) of hydrogen used. Since hydrogen is the limiting reagent you can use the ratio of hydrogen to ammonia (3:2) to figure out the number of moles of ammonia produced. 11/x=3/2 or x=(2/3) 11=7.3. Since you can't use a calculator during the mcat, you know that 6/7.3 is much greater than 50% so you can eliminate choices a and b, and d doesn't make sense because we know that the actual yeild(6) doesn't equal the theoretical(7.3). So the answer is c. I hope this helps. And more importantly I hope I'm right.

Yes, you are. Nice job.

 

[Neurolemma]

Queen of Q said it a lot better (medium pressure... never even heard of that, my knowledge must be a tad elementary!!!), but if you want a more condensed version:

The properties of an ideal gas come from the Kinetic-Molecular Theory:

(I) The molecules of the gas are spaced far apart

(II) The molecules of the gas have no interaction with each other

(III) Any collisions between the gas molecules themselves or the gas molecules & the walls of the container are elastic

On the basis of assumption (I), you can conclude that the gas is at low pressure. On the basis of (II), its clear that there are no intermolecular forces between the molecules of the ideal gas.

And of course..... the famous PV = nRT. A physical chemistry book will have the actual derivation of this. What it says is that any ideal gas can be completely described by four variables: pressure, volume, number of moles of gas, & temperature.

At low temperature & high pressure, the ideal-gas law fails because a gas begins to liquify, if I remember right.

 

[stoleyerscrubz]

Kaplan's Complete guide to the MCAT has a list of about 6 possible question stems and how to attack them. This may help you decide how to approach those questions. I just went to my local library and made notes on the 5 pages that cover this concept. Also Lukewhite( a kplan MCAT instuctor I believe) made some very good posts on question stems which I will post below.

Out of the few AAMC passages I've done, it seems like there is a certain taxonomy of question stems:

1. The main idea of the passage is ...
2. The author would most/least likely agree with ...
3. The word "..." as used in the passage refers to...

 

[C.P. Jones]

One more question guys, this one about circulation and the MCAT. In tracing the blood around the heart and to the lungs I found Kaplan's explanation to be well...krappy. The left side I think pumps the deoxygenated blood, I know there's a systole and a diastole which are the lub/dub. Blood from the lower body is from the inferior vena cava, upper superior. But I'm just having trouble piecing it all. Can someone give me a good rundown for the MCAT?

left side of the heart pumps oxygenated blood...remember, diff. b/w left side of body and left side of picture in book! go by what is your left on your own body.
I'm not going to bother saying the whole blood circulation, you can just look it up on any search engine and find many better explanations/pictures than I or Kaplan will give

 

[gotgame83]

Because Im pretty sure i wasnt supposed to ask a specific question from an aammc practice test I deleted my question.

 

[Nitya2284]

I don't think you are allowed to put actual test questions here. But I have the tests and all their solutions. I wish you told me before you purchased it because I would have given it to you free. I have the TPR soln's for 4R and can send them to you if you send me a PM.

Edited to delete quoted portion.......

Oh and thanks Q for answering my question last night for my friend.

I have 4R but I don't have the answers to them. Is there anyway I can get a hold of them..would you care??

Thanks

 

[Nitya2284]

I wanted to elaborate on "myfavred" nice concise statement. Translation begins on a free floating ribosome in the cytosol. If the nascent polypetide expresses a hydrophobic SIGNAL SEQUENCE in the first 16-30 amino acids, a signal recognition particle (SRP) will carry the entire complex to the ER. The growing protein will either be inserted into the ER lumen or threaded through the membrane of the ER.
What peptides have the SIGNAL SEQUENCE, & thus will be translated at the ER?
Proteins destined to be secreted, or end up in the "secretory pathway" will have the SIGNAL SEQUENCE. These include polypeptides that will eventually be in the lumen, or membranes of the ER, Golgi, lysomes, plasma membrane, as well as all secreted proteins.

What polypeptides will be translated in the cytosol because they lack the hydrophobic signal sequence?
Pretty much all the rest, including, proteins that will "live" in the nucleus, cytolsol, & mitochondria.

I don't think we have to know "the definition of ribosome" in this concrete detail. I don't think we are responsible for knowing this. WE were thought this in cell biology if I recall but as far as mcat is concerned a ribosome, the simplest way to put it is that ribosomal subunits, also called svedberg units are made in the nucleolus and they then attach to the mRNA. They can be either found free in the cytoplasm or attached to the ER which is then called the RER. THe process of translation is taken place via the ribosome. If the ribosome wasn't there carrying the mRNA, the TrNA couldn't bring form the anticodon-codon bond to form the protein. I don't think you're responsible for the intricate details regarding the signal sequence and polypeptide recognition.

 

[Nitya2284]

Queen of Q said it a lot better (medium pressure... never even heard of that, my knowledge must be a tad elementary!!!), but if you want a more condensed version:

The properties of an ideal gas come from the Kinetic-Molecular Theory:

(I) The molecules of the gas are spaced far apart

(II) The molecules of the gas have no interaction with each other

(III) Any collisions between the gas molecules themselves or the gas molecules & the walls of the container are elastic

On the basis of assumption (I), you can conclude that the gas is at low pressure. On the basis of (II), its clear that there are no intermolecular forces between the molecules of the ideal gas.

And of course..... the famous PV = nRT. A physical chemistry book will have the actual derivation of this. What it says is that any ideal gas can be completely described by four variables: pressure, volume, number of moles of gas, & temperature.

At low temperature & high pressure, the ideal-gas law fails because a gas begins to liquify, if I remember right.

So a real gas will behave ideally at high temperatures and low pressures or low pressure and high temperature??I'm so confused

 

[challie2385]

So a real gas will behave ideally at high temperatures and low pressures or low pressure and high temperature??I'm so confused

You are saying the same thing twice and not realizing it! Gases behave ideally at LOW PRESSURE, HIGH TEMPERATURE. Think about it...at low pressure, gases are free to take up more volume, and at high temperatures, gases are less likely to condense into liquids.

 

[Centinel]

as far as mcat is concerned a ribosome, the simplest way to put it is that ribosomal subunits, also called svedberg units are made in the nucleolus and they then attach to the mRNA.

Forgive me for being nitpicky, since the rest of your post is right on, Nitya2284. Ribosomal subunits are not called svedberg units. A Svedberg unit is used for describing sedimentation coefficients of macromolecules.

The 30S & 50S subunits of prokaryotic ribosomes are called as such because that's 'where they lie' when ultracentrifuged.

 

[Lindyhopper]

The 30S & 50S subunits of prokaryotic ribosomes are called as such because that's 'where they lie' when ultracentrifuged.

Good point. This is why when the 30S & 50S subunits are assembled the prok. ribosome is only 70S. Similiarly, the euk. subunits are 40S & 60S and assembly to form an 80S riboome.
The S units are derived from both the surface area & mass. Think of a feather floating downward. If one assembled two feathers together, there is no reason to assume that their descent would somehow be additive.

 

[Nitya2284]

Forgive me for being nitpicky, since the rest of your post is right on, Nitya2284. Ribosomal subunits are not called svedberg units. A Svedberg unit is used for describing sedimentation coefficients of macromolecules.

The 30S & 50S subunits of prokaryotic ribosomes are called as such because that's 'where they lie' when ultracentrifuged.

k that was my mistake..yeah you're right. I didn't notice that I mentioned Svedberg units.

 

[Nitya2284]

You are saying the same thing twice and not realizing it! Gases behave ideally at LOW PRESSURE, HIGH TEMPERATURE. Think about it...at low pressure, gases are free to take up more volume, and at high temperatures, gases are less likely to condense into liquids.

k right just making sure..thanks a bunch

 

[Neurolemma]

So a real gas will behave ideally at high temperatures and low pressures or low pressure and high temperature??I'm so confused

Just think of a gas in a closed cylindrical container, with a movable piston (your chem book will have a picture). The lower the piston, the greater the pressure. Keep in mind that pressure is a force: P = F/A. If the force increases while the area gets smaller, then the pressure on the gas is increasing. Now imagine that the gas absorbed some heat energy. This would mean its temperature increases. Temperature is a measure of the average kinetic energy (energy of motion)... so if the temperature increases, the kinetic energy is also going to increase. So the motion of the gas molecules is going to increase... which means the gas will push upward against the cylinder. Now the pressure on the gas molecules is going to decrease, because the A in the P = F/A is increasing. To summarize, for an ideal gas, high temperature = lots of kinetic energy = greater volume = less pressure.

 

[Nitya2284]

Just think of a gas in a closed cylindrical container, with a movable piston (your chem book will have a picture). The lower the piston, the greater the pressure. Keep in mind that pressure is a force: P = F/A. If the force increases while the area gets smaller, then the pressure on the gas is increasing. Now imagine that the gas absorbed some heat energy. This would mean its temperature increases. Temperature is a measure of the average kinetic energy (energy of motion)... so if the temperature increases, the kinetic energy is also going to increase. So the motion of the gas molecules is going to increase... which means the gas will push upward against the cylinder. Now the pressure on the gas molecules is going to decrease, because the A in the P = F/A is increasing. To summarize, for an ideal gas, high temperature = lots of kinetic energy = greater volume = less pressure.

that definitely makes sense now. Thanks!

 

[daofu]

I'm having trouble with an Examkrackers general chemistry question. Its in the EK Chemistry book (5th edition), page 43, questions 46 and 48. The two questions require a diagram so I won't bother explaining it on here. Hopefully someone with the EK books can help me out.

For question 46, correct me if I'm wrong, but the answer is D because beaker one decomposes into calcium oxide and carbon dioxide. The carbon dioxide produced in beaker one is then used to react with calcium oxide in beaker two therefore producing calcium carbonate in beaker two, because carbon dioxide is in a gas form.

As for question 48, I'm completely lost. I dont even know where to start, heh. Thanks in advance.

 

[stoleyerscrubz]

this is correct. It seems like you understand question 46. Answer A should require little thought and is wrong

answer B and C are opposite so require attention. both of them discuss the amount of Ca changing which is not possible because if you look at the equation Ca is never in the gas phase.


also at the EK website they will field questions on all of their books and MCAT based questions in general as well.

For question 46, correct me if I'm wrong, but the answer is D because beaker one decomposes into calcium oxide and carbon dioxide. The carbon dioxide produced in beaker one is then used to react with calcium oxide in beaker two therefore producing calcium carbonate in beaker two, because carbon dioxide is in a gas form.

 

[scooter31]

when studying for the mcat, i keep falling asleep, even though i got 10 hours of sleep. how do you manage to stay awake? i got myself a caramel frap so that it might help keep me awake, but i still fell asleep. when i am focused, i read for a little while, and then have to get up and walk around. this will be my 2nd time taking the mcat

how do u stay focused/awake?

the fear of applying MSTP with a sub 30 scores keeps me awake and alert...


short of that, try tea (the buzz is mellower and more prolonged) and sometimes smelling perfume/cologne gets you pepped up for a bit. That was something that my RA freshman year (10 years ago; wow, I feel old suddenly) passed along to me and its always helped.

 

[hippocampus]

the fear of applying MSTP with a sub 30 scores keeps me awake and alert...


short of that, try tea (the buzz is mellower and more prolonged) and sometimes smelling perfume/cologne gets you pepped up for a bit. That was something that my RA freshman year (10 years ago; wow, I feel old suddenly) passed along to me and its always helped.

did u drink black tea or green tea? which is better?

 

[daofu]

this is correct. It seems like you understand question 46. Answer A should require little thought and is wrong

answer B and C are opposite so require attention. both of them discuss the amount of Ca changing which is not possible because if you look at the equation Ca is never in the gas phase.


also at the EK website they will field questions on all of their books and MCAT based questions in general as well.

thanks for the reply. mm, I think I get question 46 now.

As for question 48, anyone have any insight? I'm completely lost on that question. I actually did take a look at the EK website for that question and alot of people seemed to have questions about number 48 as well. Nevertheless, after looking at Dr. Calvin's explanations on the EK website, I was still confused. I don't know where partial pressure comes into play. Basically, all I understand is that the answer is 'A' because if the partial pressure equilibrium constant is less than the partial pressure of carbon dioxide , the rxn will shift left. But it cant shift left because it needs to react with CaO, which it cant because it is removed. But my question is, isnt CaO present because its being produced by the decomposition of Calcium Carbonate in beaker one? thanks again.

 

[scooter31]

did u drink black tea or green tea? which is better?

I personally drink black (it's the UK I me), but green is just as good; if I recall, black is slightly more caffienated

 

[QofQuimica]

I'm having trouble with an Examkrackers general chemistry question. Its in the EK Chemistry book (5th edition), page 43, questions 46 and 48. The two questions require a diagram so I won't bother explaining it on here. Hopefully someone with the EK books can help me out.

For question 46, correct me if I'm wrong, but the answer is D because beaker one decomposes into calcium oxide and carbon dioxide. The carbon dioxide produced in beaker one is then used to react with calcium oxide in beaker two therefore producing calcium carbonate in beaker two, because carbon dioxide is in a gas form.

As for question 48, I'm completely lost. I dont even know where to start, heh. Thanks in advance.

Sorry, I don't have a copy of the EK book, so I can't help you based on this info you've given. Do any of you other mods have a copy of EK to help this student?

 

[G-mann]

I took the Kaplan MCAT #6 and did terrible. I got BS 7, VR 7, and PS 9. That being only a 3 point increase from my terrible 20 diag score and its been a month of studying since then. My goal is a 10 on each section (for verbal I would be happy with a 9 but at least a 2-3 pt increase on each section from what I have would be ideal for me). I am planning on taking the August MCAT but am also considering taking the April one instead. I only have 2 weeks till registration is due and I was wondering what some of you experienced ones would suggest. What do you think I should do, how should I put time into studying. I do plan to start studying a little more intensely as I have been taking it a little easy for the past month. I am taking the Kaplan class and mainly just do the readings they assign, not much more aside from some of the examkrackers material and audio osmosis. There are 5/6 weeks left to the big day, and do you think I can pull off a 2-3 point increase from what I have for each section? Thanks in advance for your responses.

(I did post this as a new thread in the MCAT forum but was not sure it was the right place to post so i'm posting the same message here. I'm brand new to the forum and find it an excellent place of valuable information)

 

[dave613]

I took the Kaplan MCAT #6 and did terrible. I got BS 7, VR 7, and PS 9. That being only a 3 point increase from my terrible 20 diag score and its been a month of studying since then. My goal is a 10 on each section (for verbal I would be happy with a 9 but at least a 2-3 pt increase on each section from what I have would be ideal for me). I am planning on taking the August MCAT but am also considering taking the April one instead. I only have 2 weeks till registration is due and I was wondering what some of you experienced ones would suggest. What do you think I should do, how should I put time into studying. I do plan to start studying a little more intensely as I have been taking it a little easy for the past month. I am taking the Kaplan class and mainly just do the readings they assign, not much more aside from some of the examkrackers material and audio osmosis. There are 5/6 weeks left to the big day, and do you think I can pull off a 2-3 point increase from what I have for each section? Thanks in advance for your responses.

(I did post this as a new thread in the MCAT forum but was not sure it was the right place to post so i'm posting the same message here. I'm brand new to the forum and find it an excellent place of valuable information)

I am taking the august mcat, like yourself. Although my story is slightly different, since i started with a 25 diag, and I have been studying hard for the past month, including now, so my suggestion is as follows: I actually am taking some of this from gujudoc, since he gave me good advice: if I were you, I would take the exam, but you should study as follows. Firstly, study intensely, take notes on what you don't understand or remember, and when you read, study very thoroughly, and take all the subject exams available in your books. Additionally, take a practice verbal exam every other day>>this is very important! You will lose some of the test taking skill, if you don't practice enough. You must do at least 3 passages every other day, and go over the answers carefully. If you keep that up, you'll hopefully be in the 30 range by the real thing.

Good luck, we're in the same boat here.

 

[stoleyerscrubz]

I reviewed those topics 3 times now so I'm going to make notecards on all of those so I can get them straight once and for all!! Maybe someone was nice enough to make a neat document on it.

Howdy,

I was just reviewing over Equilibrium and Acids and Bases. It seems to me that there are a truckload of formulas to remember.

Ones for Ksp, Keq, Kb, Ka, pKa, pKb, how they relate to eachother, pH, pOH, how to find concentration of something in a buffer solution, how to find pH with strong acids/bases, and on and on. Can someone post a concise explanation of Equilibrium and acid/base stuff? I know it seems like a lot to ask... but... yeah

 

[QofQuimica]

I reviewed those topics 3 times now so I'm going to make notecards on all of those so I can get them straight once and for all!! Maybe someone was nice enough to make a neat document on it.

We will try to do this soon. In the meantime, if you haven't already, you may want to check mcatpearls.com and see if there is some info there to help you.

 

[QofQuimica]

This thread is for students to ask and answer each other's questions for the MCAT, DAT, OAT, and PCAT subjects. All posts from the other Q & A threads that are not either students' questions or moderators' replies will be moved to this thread. Students, please post your own answers to other students' questions here in this thread--or else in the main MCAT forum--rather than in the regular Q & A threads.

If you are a pre-health (MCAT, PCAT, DAT, OAT) test prep instructor, or you have a graduate-level background in one of the MCAT subjects, or you are a senior undergrad who scored well on the MCAT, and you would like to help answer questions for one of the regular Q & A threads, please PM Shrike or me and let us know. Again, all undergrad students who are currently studying for any of these tests should NOT post answers to other students' questions in any of the regular Q & A threads. Thanks to everyone for your cooperation.

 

[Jezzielin]

Yes. http://forums.studentdoctor.net/showpost.php?p=2711972&postcount=6

I get get through to that link

 

[QofQuimica]

I get get through to that link

Hmm, not sure why; it works fine for me. Ok, I re-posted it in the gen chem topics with explanations thread anyway; it's the fifth post there in case this link won't work for you either: http://forums.studentdoctor.net/showpost.php?p=2773903&postcount=5

 

[Jezzielin]

Hmm, not sure why; it works fine for me. Ok, I re-posted it in the gen chem topics with explanations thread anyway; it's the fifth post there in case this link won't work for you either: http://forums.studentdoctor.net/showpost.php?p=2773903&postcount=5

got it thank you!!!!

 

[Jezzielin]

Nothing to do with your question, but I just wanted to say that I PM'd you something that I thought you may be able to use to prepare for the MCAT. Let me know if you got it.

I just messaged you back, thank you so much! And to think, I left SDN for 5 minutes.... tsk tsk, now I know never to leave my computer!

Thanks alot though Guju!!!