Destroyer 2011 GChem #42

[dental13]

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The question asks which of the following molecules are polar?
answer choices are follow
a.CBR4
b.SO3
c.XEF4
d.ClF5
3.PBr5

the answer is D
What I am not getting is their electron doman geometry. If you take a look at B, isn't this suppose to be little polar due to electronegativity of Oxygen? also for E, due to their electron doman gemometry (or even at molecular geometry)structure it seems like they have to be a polar molecule...

 

[p2vanlon]

The question asks which of the following molecules are polar?
answer choices are follow
a.CBR4
b.SO3
c.XEF4
d.ClF5
3.PBr5

the answer is D
What I am not getting is their electron doman geometry. If you take a look at B, isn't this suppose to be little polar due to electronegativity of Oxygen? also for E, due to their electron doman gemometry (or even at molecular geometry)structure it seems like they have to be a polar molecule...

Could be because F is More electronegative than O and there will still be a lone pair on Cl. Just a thought...dunno if it's totally right.

I will say my gut reaction was the same as yours when I saw B...I hate the questions where they give you multiple right answers and want the BEST answer.

 

[wall1two]

The question asks which of the following molecules are polar?
answer choices are follow
a.CBR4
b.SO3
c.XEF4
d.ClF5
3.PBr5

the answer is D
What I am not getting is their electron doman geometry. If you take a look at B, isn't this suppose to be little polar due to electronegativity of Oxygen? also for E, due to their electron doman gemometry (or even at molecular geometry)structure it seems like they have to be a polar molecule...

b would be non polar due to its molecular geometry. the hybridization about the sulfur is sp2 (meaning it has 3 electron "areas") and is thus planer. pairs of electrons, may they be bonding or lone pairs, want to be as far from other sets of lp or bonding electrons as possible. sulfur in b makes 3 resonance equivalent bonds making to optimum distance between the bonds 120 degrees, creating a triangle planer shape, with each "corner" of the pyramid being equal in electronegativity there is no net dipole.

if you count the total electrons in D, you will see there is 2 electrons not involved in bonding so you must place them on the chlorine. the lone pair can now be thought of as a vacancy of where a very electronegative fluorine might have been. each F in that molecule is 180* from another F balancing out the dipole.. except for 1 of the F which is 180* from the lone pair, giving the molecule a net dipole and a square pyramid shape.

 

[dental13]

your explanation was great~😀😀😀
Now I get it, So for XeF4, this one is non-polar due to it's molecular shape of square planar, it's just similar structure where it deviated from Octahedral.

Wall2Wall if you see this, I have one more question for you from destroyer 2011 Bio Q #56.

It it saying this statement is correct "glomerular filtrate is largely water and contains the same substances as blood plasma, except for large proteins."

From what I read from Cliff's AP bio, if filtrate contains erythrocytes, your kidney isn't performing correctly. The statement said same substances as blood plasma, which contains erythrocytes... how come this statement is correct?

Is erythrocytes are considered as large proteins then? hm...😎

 

[wall1two]

your explanation was great~😀😀😀
Now I get it, So for XeF4, this one is non-polar due to it's molecular shape of square planar, it's just similar structure where it deviated from Octahedral.

Wall2Wall if you see this, I have one more question for you from destroyer 2011 Bio Q #56.

It it saying this statement is correct "glomerular filtrate is largely water and contains the same substances as blood plasma, except for large proteins."

From what I read from Cliff's AP bio, if filtrate contains erythrocytes, your kidney isn't performing correctly. The statement said same substances as blood plasma, which contains erythrocytes... how come this statement is correct?

Is erythrocytes are considered as large proteins then? hm...😎

bio is not my strong suit but the trick here is you are 100% right, but this is a wording trap. blood plasma by definition is everything except the cells, (maybe platelets are in plasma , ill look into it) it is the fluid and nutrients (and waste like carbonic acid buffer system and enzymes ect) that the cells are suspended in. so your plasma contains some protines (enzymes and some AA) glucose, and a inorganic **** all of which needs to be kept in check, so it gets all filterd from the hematocrit

 

[dental13]

I see, so erythrocytes are red blood cells that is not included in blood plasma.
These questions are worded so complicated that you have to look it up and double check~ so time consuming~😡

thanks wall2wall for your help~ I know your DAT is coming up shortly.
I will definitely wait for your great breakdown with great scores!
Mine is at May 12... 😱

 

[Teeth12345]

dental13, wall is absolutely right. Platelets are considered cells and along with leukocytes and erythrocytes, do NOT enter the Bowman's Capsule. They are not filtered. What helps me is that I view Blood as a whole entity comprised of 4 components.

Blood --> Erythrocytes + Leukocytes + Platelets + Plasma

Plasma is tricky because it is the non-cell portion (it does not contain platelets). The important thing to note about plasma is that although it is not composed of erythros, leukos, and platelets, it CARRIES them. Obviously the cells need something to flow in through the body and that something is plasma.

I hope I didn't make this sound confusing. I don't think the actual DAT questions will be worded so trickily (I hope not!)

 

[wall1two]

thanks for the support, from my practice so far i feel like the bio is like the keyhole part of the pat, i plan to go through it once at a medium speed take my time on the chem and orgo then come back to the bio. just like the keyholes i find with a second perspective you catch things you didn't the first time. i feel like the hardest part is actually just deciphering the questions!