Achiever/kaplan Questions!

[MansonTiles]

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I was thinking, I am doing ok on these exams, BUT, would love some extra help/explanations on some questions from you all. I am willing to post random questions from the DAT achiever exams and similar ones OFTEN so everyone can see and get help if they have questions!
🙂

1. Which of the following compounds will have its proton(s) shifted furthest and downfield on a 200 MHz 1H NMR spectrum?

A. CH3CH3
B. CH3CI3
C. CH3I
D. CH2I2
E. CHI3

2. Determine the value of x if 10.0 g of CuSO4.xH2O have been dehydrated to 6.4 g of anhydrous CuSO4.

A. 3
B. 4
C. 5
D. 6
E. 7

3. What is the net ionic equation for the reaction between FeS and HCl?

thanks and bye all 🙂

 

[mo magic carpet]

the answer to number 2 is

5

number of moles of cuso4 is 6.4/160= 0.04

number of moles of h20= 3.6/18= 0.2

.2/0.04=5

 

[lifeisgood]

I was thinking, I am doing ok on these exams, BUT, would love some extra help/explanations on some questions from you all. I am willing to post random questions from the DAT achiever exams and similar ones OFTEN so everyone can see and get help if they have questions!
🙂

1. Which of the following compounds will have its proton(s) shifted furthest and downfield on a 200 MHz 1H NMR spectrum?

A. CH3CH3
B. CH3CI3
C. CH3I
D. CH2I2
E. CHI3

2. Determine the value of x if 10.0 g of CuSO4.xH2O have been dehydrated to 6.4 g of anhydrous CuSO4.

A. 3
B. 4
C. 5
D. 6
E. 7

3. What is the net ionic equation for the reaction between FeS and HCl?

thanks and bye all 🙂

Not sure if these are right but I'll try.

1. I would say E... because electron withdrawing groups cause the electrochemical shift of protons to move further downfield. In this case, the 3 I- ions that are in contact with the SAME carbon as the one proton (in answer E) would have the greatest shielding effect.


2. I agree with Mo magic...

3. Again, not sure but I think it is

FeS (s) + 2H+ ---> H2S (g) + Fe2+

Net ionic equations only involve the species that participate in the chemical reaction. Since Cl- is soluble in both instances, it can be removed from the equation. (i.e. HCl (aq) & FeCl2 (aq) )

 

[RozhonDDS]

I was thinking, I am doing ok on these exams, BUT, would love some extra help/explanations on some questions from you all. I am willing to post random questions from the DAT achiever exams and similar ones OFTEN so everyone can see and get help if they have questions!
🙂

1. Which of the following compounds will have its proton(s) shifted furthest and downfield on a 200 MHz 1H NMR spectrum?

A. CH3CH3
B. CH3CI3
C. CH3I
D. CH2I2
E. CHI3

2. Determine the value of x if 10.0 g of CuSO4.xH2O have been dehydrated to 6.4 g of anhydrous CuSO4.

A. 3
B. 4
C. 5
D. 6
E. 7

3. What is the net ionic equation for the reaction between FeS and HCl?

thanks and bye all 🙂

#1) the answer is E, because the more electronegative/halogens, attached to the ch3, means its moves farther downstream, if their was an answer that had chI4, than that would be the right answer because there are more halogens, thus pushing it further downstream.

 

[armorshell]

#1) the answer is E, because the more electronegative/halogens, attached to the ch3, means its moves farther downstream, if their was an answer that had chI4, than that would be the right answer because there are more halogens, thus pushing it further downstream.

Only problem with that is CHI4+ would put 5 bonds on carbon, and thus be incredibly unstable...and CI4 wouldn't register any signal on a H1-proton NMR 🙂

 

[mannythemanatee]

does anybody know #3?

3. What is the net ionic equation for the reaction between FeS and HCl?

 

[MansonTiles]

the answer to 3 is.....

FeS(s) + 2H+(aq) >> H2S(g) + Fe2+(aq)

BUT, i just dont know how to go about doing these kinds of problems and breaking them down to ions and then figuring out whats soluble, spectator ions..?????
how do you guys do this one from the beginning?

 

[lifeisgood]

..

 

[lifeisgood]

...

 

[lifeisgood]

the answer to 3 is.....

FeS(s) + 2H+(aq) >> H2S(g) + Fe2+(aq)

BUT, i just dont know how to go about doing these kinds of problems and breaking them down to ions and then figuring out whats soluble, spectator ions..?????
how do you guys do this one from the beginning?

You have to know solubility rules!!!! I knew that FeS was solid and that the only plausible reaction was formation of H2S, which you should also know is a (highly toxic) gas. The other thing you need to know is that HCl is soluble and FeCl is soluble. SInce the choride ions exist on both sides of the equation you can cancel them out. The entire equation is as follows:

FeS (s) + 2H+ (aq) + 2Cl- (aq) ----> H2S (g) + Fe2+ (aq) + 2Cl-(aq)

You would then delete those items appearing identical on both sides. The only species here that is the same is Cl-....So the NET IONIC EQUATION would be:

FeS (s) + 2H+ (aq) ----> H2S (g) + Fe2+ (aq)

 

[MansonTiles]

thank you lifesgood. good explanation 🙂

4. If three identical anticodons of GAU are found matching consecutively along an mRNA frame, what will be the corresponding base sequence on the original DNA stretch?

A. CUACUACUA
B. CTACTACTA
C. CUTCUTCUT
D. GAUGAUGAU
E. GATGATGAT

it says the answer is E! how is this...and not B??
B is the DNA frame for the mRNA codon shown, GAUGAUGAU, right?


I will be listing more VERY SOON.
thanks for all the help. 🙂

 

[Notoriousjae]

thank you lifesgood. good explanation 🙂

4. If three identical anticodons of GAU are found matching consecutively along an mRNA frame, what will be the corresponding base sequence on the original DNA stretch?

A. CUACUACUA
B. CTACTACTA
C. CUTCUTCUT
D. GAUGAUGAU
E. GATGATGAT

it says the answer is E! how is this...and not B??
B is the DNA frame for the mRNA codon shown, GAUGAUGAU, right?


I will be listing more VERY SOON.
thanks for all the help. 🙂

ok this is very easy
You are given the sequence on the mRNA which is 5'GAUGAUGAU3'
So you have
5'GAUGAUGAU3' mRNA
3'CTACTACTA5' template strand of DNA
5'GATGATGAT3' coding strand of DNA <-- correct answer

know that there are 2 strands of DNA, the question is asking you for the base sequence on the original strand of DNA which is the coding strand and not the anti sense strand or template strand hence the answer is E

 

[MansonTiles]

very nice, thanks! 🙂

 

[armorshell]

thank you lifesgood. good explanation 🙂

4. If three identical anticodons of GAU are found matching consecutively along an mRNA frame, what will be the corresponding base sequence on the original DNA stretch?

A. CUACUACUA
B. CTACTACTA
C. CUTCUTCUT
D. GAUGAUGAU
E. GATGATGAT

it says the answer is E! how is this...and not B??
B is the DNA frame for the mRNA codon shown, GAUGAUGAU, right?


I will be listing more VERY SOON.
thanks for all the help. 🙂

I don't know about you, but when I took the test, I read the question as "3 anticodons to GAU." Maybe you did the same?

 

[MansonTiles]

5. Which of the following hybridizations does the Be atom in BeH2 assume?

a. sp
b. sp2
c. sp3
d. none above

OK, it says its A....but how in the H is that when the Be atom is sp3 because of the single bonds to the hydrogens?

it says that the Hydrogens are 180 apart and thats why its sp, but still dont understand when I thought that sp, sp2, sp3 had to do with number of bonds?
sp-180, sp2-120, sp3-109.5?

like CH4, all sp3, single bonds.
like ethyne, sp, triple bond.