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This thread shall serve as the official site for discussion of the AAMC Self-Assessment in MCAT Physical Sciences.
I'll start:
For #80, anybody have a quicker strategy to get to the answer?
Since level of intensity for sound B is 20 db greater than sound A, I just did the following:
20=10*log(Intensity of B/Intensity of A)
2=log(Intensity of B/Intensity of A)
10^2=Intensity of B/Intensity of A
100(Intensity of A)=Intensity of B
Not sure if this is the proper way to doing this type of question...
Did anyone do the Physics Self-Assessment yet? And how about Gen Chem Self-Assessment?
I did both of them (and Ochem) and I'm kinda pissed about the score
Lets discuss the scores so I get some peace of mind that I'm not the only one doing bad.
#107
Electric power for transmission over long distances is "stepped up" to a very high voltage in order:
A) to produce currents of higher density
B) to produce higher currents in the transmission wires
C) to make less insulation necessary.
D) to cut down the heat loss in the transmission wires.
The answer is D and the explanation given is a bit confusing.
Is this basically saying since we can maximize the power at user's end by maximizing either V or I, and Power lost is also V^2/R=I^2*R, it's better to maximize V than I to minimize heat loss? Since R is constant and P_lost is minimized by having R in the denominator?
What is the significance of the van t hoft factor in question 95? Why do you not take it into account here?
Gonna try and revive this question, I'm also confused why the solution didn't account for the "i" factor
Based only on the information in the passage, which of the following expressions should be used to best estimate the temperature at which ice will form
A) 0 - 1.86(6.020)
B) 0 - 1.86(1.025)
C) 0 - 1.86(4.184)
D) 0 - 1.86(1.142)
The answer is D, but I chose A since it's the closest to 5*1.142.
i = 5, since there's 5 ions in solution of seawater
Anyone care to explain this?
Heya, my response here:
http://forums.studentdoctor.net/threads/aamc-questions-the-whole-thread-is-spoilers.1057364/
Just scroll to the bottom
Thanks for the reply
So essentially, because we were given the molality of each ion species, we can omit the van't hoff factor simply because its already contained in the molalities of each ion?
"The solubility of calcium sulfate would be expected to be low in water because both ions are highly charged." Can someone please elaborate on this? I don't understand why calcium sulfate is poorly soluble in water even though it is an ionic compound.
Thank you everyone!
Merged with Official PS Self-Assessment Thread."The solubility of calcium sulfate would be expected to be low in water because both ions are highly charged." Can someone please elaborate on this? I don't understand why calcium sulfate is poorly soluble in water even though it is an ionic compound.
Thank you everyone!
A nucleus splits into two fragments that have equal charge but unequal mass. Which of the following is equal for the two fragments as they move apart?
A) Magnitude of the force of one fragment on the other
B) Magnitude of acceleration
C) Speed
D) Kinetic energy
The answer was A. I was able to cross off B and C pretty quickly, however I do not understand why D is incorrect. If the two fragments have different masses, they can still have the same kinetic energy (as long as they have different speeds). Am I wrong in assuming this? Any input would be great.
To answer the question their accelerations are different, even if their forces are the same. This means their velocities will be different as well as time progresses. Thus the reason their kinetic energies are also different.
Oh, that's right. I think I was confusing momentum with kinetic energy. Two objects with equal momentums can still have different kinetic energies. Thanks for the reply!
No idea lol, I remember I missed this one too.Physics Self Assessment
#39
Modern nuclear reactors typically have several boron rods that can be inserted varying degrees into the reactor. These rods control the rate of the reaction by:
A. producing neutrons
B. speeding up neutrons
C. reflecting neutrons
D. absorbing neutrons
How were we suppose to know the answer to this? (I know what the answer is. My question is how were we suppose to figure it out?)
The chemical bonds that actually hold the atoms together are electrostatic interactions; they have nothing to do with magnetism.Physics Self Assessment
#93
What mechanism supplies the tension in the string at the molecular level?
Why isn't the answer magnetic forces?
Stretching bond lengths seems to be the RESULT of the "mechanism" that supplies tension in the string, NOT the cause. Please explain if you can.
Impurities aren't considered part of the substance itself; that is, they won't be represented in the molecular formulae. If they were, the precise amount of impurity would determine the formula since the empirical formula would depend directly on the ratio of mineral : impurity, and you'd have infinite molecular formulae for varying degrees of impurity.General Chemistry Self Assessment
#82
Limestone, marble, caulk, Iceland spar are all composed of CaCO3 crystals. Which of the following could cause differences in the properties of the material:
I. Crystal Grain Size
II. Conditions of Formation
III. Molecular Formula
IV. Impurities
Doesn't it stand to reason that if "impurities" are present, the molecular formula may vary?
The question tells you you're adding Ca2+ to a solution of Ca2+ and (CaO3)2–, so those are the reactants and the product being formed in CaCO3. Also, this is the standard format for a solubility equilibrium from which the Ksp expression is written. Edit: I misspoke here. Solubility equilibria represent the dissolution, going left to right, of solid to ions. See next post for for info.General Chemistry Self Assessment
#91
The addition of Ca2+ to a solution containing Ca2+ and (CaO3)2- ions causes CaCO3 to precipitate because:
C. The reaction quotient Q would be lower than the Ksp
D. The reaction quotient Q would be greater than the Ksp
Doesn't the answer to this depend on which direction you write the reaction? If so, how do you determine whether the test maker wants you to write CaO3 ---> Ca2+ + (CaO3)2- OR Ca2+ + (CaO3)2- ---> CaO3 ????
No idea lol, I remember I missed this one too.
The chemical bonds that actually hold the atoms together are electrostatic interactions; they have nothing to do with magnetism.
Impurities aren't considered part of the substance itself; that is, they won't be represented in the molecular formulae. If they were, the precise amount of impurity would determine the formula since the empirical formula would depend directly on the ratio of mineral : impurity, and you'd have infinite molecular formulae for varying degrees of impurity.
The question tells you you're adding Ca2+ to a solution of Ca2+ and (CaO3)2–, so those are the reactants and the product being formed in CaCO3. Also, this is the standard format for a solubility equilibrium from which the Ksp expression is written.
I misspoke on the last question, sorry. The Ksp expression is always just a product of ion concentrations, so the equilibrium is of course written from solid to aqueous phases going left to right. Because of this convention the Q exceeds Ksp leading to precipitation of the solid.Thank you very much. These are very difficult questions and I think you did an excellent job of explaining all but the first one and maybe except the last one* I listed as well. I figured that there was a chance that no one knew the answer, so I feel relieved.
*I think #91's answer key said, "CaCO3 ---> Ca + (CaO3)2"
No idea lol, I remember I missed this one too.
The chemical bonds that actually hold the atoms together are electrostatic interactions; they have nothing to do with magnetism.
Impurities aren't considered part of the substance itself; that is, they won't be represented in the molecular formulae. If they were, the precise amount of impurity would determine the formula since the empirical formula would depend directly on the ratio of mineral : impurity, and you'd have infinite molecular formulae for varying degrees of impurity.
The question tells you you're adding Ca2+ to a solution of Ca2+ and (CaO3)2–, so those are the reactants and the product being formed in CaCO3. Also, this is the standard format for a solubility equilibrium from which the Ksp expression is written. Edit: I misspoke here. Solubility equilibria represent the dissolution, going left to right, of solid to ions. See next post for for info.
To answer the question their accelerations are different, even if their forces are the same. This means the difference in their velocities will be greater as time progresses. Hence the reason their kinetic energies are also different.
Are you able to make any conclusions about which object (higher mass object or lower mass object) would have greater KE given the same initial force?
Or does it depend on the numbers given?