gen chem questions

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heshyn2000

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Guys I came across some unique questions, anyone up for the challenge?
1) How much more acidic is a solution of PH = 2 than one at PH = 6 ?
2) Find the PH of a 1.0* 10-13 M HCL solution?
Good Luck!
 
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heshyn2000 said:
Guys I came across some unique questions, anyone up for the challenge?
1) How much more acidic is a solution of PH = 2 than one at PH = 6 ?
2) Find the PH of a 1.0* 10-13 M HCL solution?
Good Luck!
Click to expand...

1) I'd say 10,000 times more acidic

2) depends, is it 10 ^ (10-13) OR 1 * 10-13 OR (1 * 10) - 13.....?
 
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heshyn2000 said:
Explian why
Click to expand...

send me a pm via aim in about an hour or 2...I don't want to confuse people here..
I can tell you that I am 100% sure about my answer.
Challenge me more...So far easy questions
 
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1) why are boiling points a better indication of intermolecular bonding than melting points?
2) Find the amount of H2O nedded to dilute 400ml. of .8M to 2.0M ?
 
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heshyn2000 said:
1) why are boiling points a better indication of intermolecular bonding than melting points?
2) Find the amount of H2O nedded to dilute 400ml. of .8M to 2.0M ?
Click to expand...

#1)
because once in the gaseous state, relatively, they are so far away from each other such that, relatively, they no longer exert much intermolecular forces on each other. remember F = GMm / r^2 so technically even gases that are miles away exert some sort of force on each other albeit not strong....
Solid to liquid --> in both states, everything is pretty close....

#2) impossible...you are not diluting... 2 M > 0.8 M
 
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heshyn2000 said:
Ooops wrong, both are the same. remember solubilty has nothing to do with the size.
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OH - C - C - C - C - C - C - OH has more intermolecular forces in the hydrocarbon portion...we have more interactions between OH - C - C - C - C - C - C - OH molecules....stronger wan der wall forces

I still think OH-C-C-C is more soluble in water...
 
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OK, if you know this I'm sure you'll score in the high 20"s if not 30. Which solution has the highest osmotic pressure, and why?
1) 1 M NACL (aq)
2) 1.5 M CACl2 (aq)
3) 2.0 M KNo3 (aq)
4) 3.0 M C6H12O6 (aq)
 
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OK, I guess he's not here now...so, I believe it's choice 2 because it dissolves into one calcium ion and 2 chloride ions, which gives a molarity of 4.5M and gives it the greatest osmotic pressure, since osmotic pressure = (M)(R)(T).
 
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heshyn2000 said:
OK, if you know this I'm sure you'll score in the high 20"s if not 30. Which solution has the highest osmotic pressure, and why?
1) 1 M NACL (aq)
2) 1.5 M CaCl2 (aq)
3) 2.0 M KNo3 (aq)
4) 3.0 M C6H12O6 (aq)
Click to expand...


B is the correct answer. Sorry for late reply. I had to step out for a while. I was so stressed out.

pv = nRT -> p = MRT and then we have to add the van hof factor to the formula
so the equation becomes p = iMRT. R & T are constant in all 4 cases.
So the one that has the biggest i * M is the answer and in this case B is the answer...

please, give harder questions. So far everything is very easy. 🙂 😉 😉 🙂

side note: I don't think I'll get a good score for G'Chem 😡
 
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Lemmie ask one😛
You got Ch3-Ch2-Ch2=Ch-Ch3
If you add some hydrogen to it with catalyst etc, where does the FIRST hydrogen add too?, in practice, 😛
I don't know if this is on your MCAT thing , but lets see if you can figure it out 😉
 
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dinesh said:
Lemmie ask one😛
You got Ch3-Ch2-Ch2=Ch-Ch3
If you add some hydrogen to it with catalyst etc, where does the FIRST hydrogen add too?, in practice, 😛
I don't know if this is on your MCAT thing , but lets see if you can figure it out 😉
Click to expand...


My guess is that the 1st hydrogen can land on carbon 2 or carbon 3 (equally likely). In both cases, the stability of the intermediate will be the same.
 
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dinesh said:
Lemmie ask one😛
You got Ch3-Ch2-Ch2=Ch-Ch3
If you add some hydrogen to it with catalyst etc, where does the FIRST hydrogen add too?, in practice, 😛
I don't know if this is on your MCAT thing , but lets see if you can figure it out 😉
Click to expand...
Are you sure your question is correct? looks like carbon #3 has 5 bonds.
but i agree with datstudent.
 
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heshyn2000 said:
Very nice, you hit the nail on its head. How about orgo ?
Click to expand...

I thought you were going to challenge me with much more difficult questions...what happened? come on, give a very hard question...
 
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OH-C-C-C
is more soluble it has a net dipole moment (even tho OH is basic on this akyl chain the oh makes it slightly acidic) and like dissovles like rite
the longer alkyl chaing has more intramolecular forces (london forces) and some hydrogen bonding, however when put in water the chaing must overcome the london forces to participate hydrogen bonding with h20....the smaller one has less dispersion forces to over come allowing it to dissociate better polar h20
 
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SunnyD0119 said:
OH-C-C-C
is more soluble it has a net dipole moment (even tho OH is basic on this akyl chain the oh makes it slightly acidic) and like dissovles like rite
the longer alkyl chaing has more intramolecular forces (london forces) and some hydrogen bonding, however when put in water the chaing must overcome the london forces to participate hydrogen bonding with h20....the smaller one has less dispersion forces to over come allowing it to dissociate better polar h20
Click to expand...

That's exactly what I said but I think it's intermolecular NOT intramolecular...
 
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dat_student said:
I thought you were going to challenge me with much more difficult questions...what happened? come on, give a very hard question...
Click to expand...
Here you go datstudent.
A given mass of gas in a rigid container is heated from 100C to 500C. Which of the following responses best describes what will happen to the pressure of the gas? Explain your answer.
1) The pressure will remain the same.
2) The pressure will decrease by a factor of five.
3) The pressure will increase by a factor of five.
4) The pressure will increase by a factor less than five.
5) The pressure will increase by a factor greater than five.
 
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heshyn2000 said:
Here you go datstudent.
A given mass of gas in a rigid container is heated from 100C to 500C. Which of the following responses best describes what will happen to the pressure of the gas? Explain your answer.
1) The pressure will remain the same.
2) The pressure will decrease by a factor of five.
3) The pressure will increase by a factor of five.
4) The pressure will increase by a factor less than five.
5) The pressure will increase by a factor greater than five.

Which of the following species is isoelectronic with Kr?
1) Xe
2) K+
3) In 3+
4) S2-
5) Sr2+
Click to expand...


cheesy questions...anybody can do these..I pass 'em to others 🙂 😉
 
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dat_student said:
cheesy questions...anybody can do these..I pass 'em to others 🙂 😉
Click to expand...

Yeah, if these questions and the Kaplan flashcards represent the difficulty of the DAT I should be a very happy girl (I think I might stop torturing myself with Examkracker 1001 chemistry questions).

Electronegativity of Be = 1.5, while O = 3.5. I read that it is molecular somewhere in Kaplan or Examkrackers, though. Page 915 of Zumdahl Chem text says that while the other oxides of Group IIA metals are highly ionic, BeO has "considerable covalent character". So, I figured it's a good exception to point out.
 
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mochafreak said:
Yeah, if these questions and the Kaplan flashcards represent the difficulty of the DAT I should be a very happy girl (I think I might stop torturing myself with Examkracker 1001 chemistry questions).

Electronegativity of Be = 1.5, while O = 3.5. I read that it is molecular somewhere in Kaplan or Examkrackers, though. Page 915 of Zumdahl Chem text says that while the other oxides of Group IIA metals are highly ionic, BeO has "considerable covalent character". So, I figured it's a good exception to point out.
Click to expand...

2 seems a big enough difference to make it ionic. Based on what you said I guess I am wrong. Honestly, for ionic/covalent bonds, I don't know what the cut off point is. I just use the general trend for this sort of question. I am NOT so good at memorizing a lot of numbers because they usually end up overwhelming my hippocampus :laugh: :laugh:
 
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dat_student said:
cheesy questions...anybody can do these..I pass 'em to others 🙂 😉
Click to expand...
datstudent, the DAT is a straightforward test, and these are what the gen chem. questions look like. so if you know these cold, your good to go.
Hey, for the fun of it, explain the answer to question # 1.
 
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dat_student said:
2 seems a big enough difference to make it ionic. Based on what you said I guess I am wrong. Honestly, for ionic/covalent bonds, I don't know what the cut off point is. I just use the general trend for this sort of question. I am NOT so good at memorizing a lot of numbers because they usually end up overwhelming my hippocampus :laugh: :laugh:
Click to expand...

I read it in examkrackers, which I generally trust...I agree that the electronegativity difference seems large enough to make it ionic. Zumdahl's says that the covalent character is due to the Be being able to polarize the charge on the oxygen effectively. Which also doesn't make much sense because Be is small and larger elements like I are better able to polarize charge, right? That's why Iodine is more nucleophilic than Flourine, right?
 
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heshyn2000 said:
datstudent, the DAT is a straightforward test, and these are what the gen chem. questions look like. so if you know these cold, your good to go.
Hey, for the fun of it, explain the answer to question # 1.
Click to expand...

I'd like to thank you for posting these questions, because if they really do mirror the difficulty of the DAT I was wasting my time doing really difficult chem questions.
 
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heshyn2000 said:
Here you go datstudent.
A given mass of gas in a rigid container is heated from 100C to 500C. Which of the following responses best describes what will happen to the pressure of the gas? Explain your answer.
1) The pressure will remain the same.
2) The pressure will decrease by a factor of five.
3) The pressure will increase by a factor of five.
4) The pressure will increase by a factor less than five.
5) The pressure will increase by a factor greater than five.
Click to expand...

ok, I guess this is question #1

rigid container-> so volume is constant.

P1/T1 = P2/T2
P1/373 = P2 / 773
P2/P1 = 773/373 = 2 (approximately)

So, 4 seems to be the right answer.
 
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