aamc cbt11 thread

[sekistudent]

Can we start an official aamc cbt11 thread. I took this test a few days ago and have some questions. Can I just start this thread? Or, is that sort of behavior for the more senior members.

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[Cawolf]

Also, since it is a 'compact' object, doesn't that mean air resistance is not acting on it as much hence why it can be ignored? What is the reasoning behind why C would be eliminated?

The key here is that they want the "best" explanation - not any correct one.

The drag force is proportional to the square of the velocity. When an object only accelerates a short distance, it's velocity remains low, and the drag force is minor.

Answer C may be correct if the object is very dense and aerodynamic, but we don't know that. So whereas this may be true, it is certainly not the best answer.

 

[sanguinee]

This question does not really require any specifics.

The NiF2 contributes the reactants for the precipitation reaction - which is equilibrium dependent on the concentration of the reactants. To determine which compound will precipitate first, we need to know how much of what reactants we start with.

Ah, so concentration of MgSO4 would be relevant also, if it was an answer choice. I need @Cawolf to fit in my head while I take the mcat tbh

 

[Cawolf]

Ah, so concentration of MgSO4 would be relevant also, if it was an answer choice. I need @Cawolf to fit in my head while I take the mcat tbh

Exactly. The solubility is extremely high in water though, so we expect it to dissociate to near completion - making it's solubility not that useful.

Haha. I don't know if that would be an advantage. Still waiting to see how I did on my own test.

 

[Buzzin]

PS #20. The compressive bone strength of human bone is 2.0 x 10^8 N/m^2. What crushing mass, supported by an upright forearm, would cause a 1% change in length of a 5-cm^2 cross-sectional area of forearm bone?

Equation for Young's Modulus given as E = (F/A) / (delta L / L) so I rearrange and solve for F, but how do I KNOW that F = mg in this example?

 

[Cawolf]

What other sort of force caused by a mass do you know?

edit: That reads more sarcastic than intended. Gravity is the only possible answer though.

 

[Buzzin]

Binding Energy, Momentum, not that they apply but I guess that is the only way to look at it. Not very familiar with examples of Young's modulus.

 

[Cawolf]

None of the prior things you listed are forces.

If a passage wants a force caused by a mass, it is gravity.

I suggest a quick a review of the four fundamental forces.

 

[Buzzin]

Binding Energy is part of the Strong Force, is it not?

 

[Cawolf]

Binding Energy is part of the Strong Force, is it not?

Yup. E = (Δm)c^2

 

[m25]

Binding Energy is part of the Strong Force, is it not?

Yup. E = (Δm)c^2

I've never heard of the term strong force before, but binding energy's unit is in Joules so it's energy, not force. So then why is it called the strong "force"?

 

[Cawolf]

@m25

Force is the negative derivative of the potential energy.

 

[m25]

@m25

Force is the negative derivative of the potential energy.

What do you mean?

 

[Cawolf]

I just mean that force is inherently related to the potential energy of a system.

If you haven't taken physics or a little calculus it is hard to explain. It is also beyond the scope of this discussion.

The broadest way to explain it would be to say that energy is the capacity for something to do work. Work involves the application of a force. So the concepts are inherently related. The binding energy is the energy required to overcome the strong nuclear force.

 

[m25]

For physical section #33:
The maximum mass of H2(g) that would be expected to form by the reaction of 6.54 g Zn(s) with 50.0 mL of 0.1 M HCl is equal to which of the following?

We are first required to balance the equation which turns out to be
Zn(s) + 2HCl(aq) → H2(g) + ZnCl2(aq)

But how are we supposed to know that Zn will be 2+ oxidization state and therefore form ZnCl2 as opposed to ZnCl or something??

 

[Cawolf]

@m25

Zinc is always +2, but you don't need to know that for the question.

The solution you are starting with contains only 0.005 g of Hydrogen, so that is the greatest amount of H2 that can be produced.

 

[m25]

@m25

Zinc is always +2, but you don't need to know that for the question.

The solution you are starting with contains only 0.005 g of Hydrogen, so that is the greatest amount of H2 that can be produced.

But without knowing the overall reaction first, I can't determine which is the limiting agent right?

 

[Cawolf]

You can, because you start with 0.1 moles of Zinc and 0.005 moles Hydrogen and Chloride - that is 20 times more Zinc.

So unless the product is ZnCl21 (which it obviously is not) - the Zinc will not be limiting.

It seems like you are trying to make the problem more complicated than it is. Getting the moles of each should be quick. Simply comparing the magnitude of each number will show you the HCl is limiting.

 

[krukshanks]

But without knowing the overall reaction first, I can't determine which is the limiting agent right?

You should memorize that Zn comes out as 2+ though. This is almost a common-sense-level point. I'd say get familiar with the valence of common metal elements, such as K, Ca, Na, Mg, Al, Zn, Fe, Cu, Hg, Ag. (Most of the valences in the p block can be obtained from periodic table though.)

 

[drechie]

Lipid-soluble toxins must be oxidized before they are excreted. Otherwise, the toxins could NOT pass through the:

Bowman's capusule
Cell membrane
Red Blood Cell
cytoskeleton

i thot it was either bowman's or red blood cell (dont fatty acids move through the circulation system via albumin in RBCS?) after entering the circ. system through the lympatic. What is a good way to think about this?