2009 Sample questions help

[Member 139582]

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Hey guys,

Just took the 2009 ADA exam and I was confused on these questions, if you don't mind clarifying what they are:

1) Which is the major intracell. buffer:
Tris
Acetate
Bicarb.
Phosphate

I am assuming this is Bicarbonate? Although I thought that was the buffer for the blood, and intracellular was phosphate, but I could be wrong.

2) Which protein is normally involved in receptor mediated endocytosis?
Desmin
Tubulin
Clathrin - I am assuming this is the answer, but I had no idea what these words mean, this is so left-field 🙁
Spectrin
Hyaluronidase


3) Although entropy continually increases within the universe as a whole, developing organisms gradually become more organized. What are these organisms capable of doing to aid this process?

a- Lowering activation energy with enzymes
b - Violating the Second Law of Thermodynamics
c - Using external sources of energy
d - concentrating their own molecules so that energy flow is reversed
e - creating energy

I put d but its wrong, would it be c? I can't think of any examples. Also what does d even mean?


4) If 50.0 mL of H 2 SO 4 required 50.0 mL of 1.0 M NaOH for a complete neutralization reaction, according to the equation shown below, what would be the molarity of an acid? (2NaOH + H 2 SO 4 → Na2SO4 + 2H2O)
a - .33
b - .5
c - 1 - I said 1M but this was wrong?
d - 2
e - 4

So for this, does the coefficients of a given rxn not matter when calculating Normality in a neutralization? Because the answer will be 1M (what I had) if you include the 2 in front of the NaOH rxn, but .5M answer if you don't include the 2 from the NaOH rxn. Essentially does the Normality of NaOH remain 1, or change to 2 because of the coefficient in the rxn?

Also got a 19/20/19 for Bio/GC/OC, kind of anxious now for my exam :/

Let me know what you guys think, thanks in advance.

 

[ecap707]

First question def phosphate
Second question is clathrin, it's a protein that helps form vesicles at the cell membrane
Third question pretty sure it's A. Enzyme use is the main reason we are able to become so complex. The other options seem less likely
Fourth question . My chemistry is rusty but I'll take a stab. X = 2 co eff x 1 M x 50 ml / 50 ml = 2 M. But I'm not really sure

 

[zzto]

3 is C 🙂

 

[Member 139582]

Thanks for your input guys. Does anyone mind clearing up question 4 for me?

 

[panmit]

Hey number 4, the easiest way to do these problems is using normality or just finding equal moles of acid and base.

You could also use the method of stoichiometry and use the coefficients to solve this answer as well.

 

[chemkay]

3 is C (I think anyways) And when asking for the molarity of an acid you have to take into account if it's a mono protic, diprotic, ect acid. H2SO4 is a diprotic acid because it has 2 H's. So just set up the equation m1v1(i)=m2v2(i)
Where i is taking into account how many hydrogens each has

(.05L)(2)(x)=(.05L)(1)(1M)
Solve for X and you get 0.5M H2SO4

 

[chemkay]

Here is a link to someone else answering it if my explanation doesn't make sense:

http://forums.studentdoctor.net/threads/titration-neutralization-problem-is-2009-ada-wrong.845507/

 

[bamtori]

4) If 50.0 mL of H2SO4 required 50.0 mL of 1.0 M NaOH for a complete neutralization reaction, according to the equation shown below, what would be the molarity of an acid? (2NaOH + H2SO4 → Na2SO4 + 2H2O)
a) .33
b) .5
c) 1
d) 2
e) 4

Answer:
N1V1=N2V2
(2)(50mL)(x) = (1)(50mL)(1M)
x=1/2 or 0.5M
*ignore the coefficients when calculating N1V1=N2V2. N is the number of H+ or OH- ions that the molecule will give off.
For H2SO4, N=2 (2 H+)
For NaOH, N=1 (1 OH-)

If you have Destroyer, refer to question #135 in the Gen Chem section and read the solution!

 

[Member 139582]

That clears it up thanks for your help guys! I will ignore the coefficients then.