General Chemistry - Solutions & Intermolecular Forces (HW Help)

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katrina007
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Hi,

I need some help with my homework. I have three questions which I'm not quite sure which answer it is, though I give it my best try. If anyone can help, it'll be much appreciated. Thanks in advance...

Question One:
Which of the following substances will have hydrogen bonds between molecules?
a) (CH3)3N
b) CH3-O-CH3
c) CH3CH2-OH
d) CH3CH2-F
e) HI

** (e) can't be the answer becuz it doesn't have any Hydrogen Bonds (N,O,F)
** (a) can't be the answer becuz the N atom is by itself. H atom is attached to C atom and therefore can't bond with the N atom. Same with letter (d)

I think the answer is c... Plez correct me if I'm wrong.

Question Two:
Which of the following should have the highest boiling point?
a) CF4
b) CCl4
c) CBr4
d) CI4
e) CH4

** I think the answer if (a) becuz of the Hydrogen Bonding forces being the strongest of all forces and therefore has highest boiling point. Plez tell me know if this is the right answer or not and explain why - (if possible)

Question Three
A solution of Sucrose (sugar) in water in in equilibrium with solid sucrose. If more solid sucrose is now added, with stirring,
a) the concentration of the solution will increase
b) the concentration of the solution will decrease
c) the concentration of the solution will remain same
d) the volume of solution will increase
e) a supersaturated solution will be produced.

** (c) can't be the answer becuz something is being added so it has to change - cannot remain same. I took a guess on this one and I think its letter (a). Again please tell me if I am wrong or correct. and explain if possible.


Answers to anyone or all of these questions will be greatly appreciated. Need this 3 homework probs. done by tomorrow. Again, thanks in advance.

Regards,
Katrina
 
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Hello again,

Sorry to bump up this thread but please anyone out there that can help me with this 3 or anyone question(s)?
 
katrina007 said:
Hi,

I need some help with my homework. I have three questions which I'm not quite sure which answer it is, though I give it my best try. If anyone can help, it'll be much appreciated. Thanks in advance...

Question One:
Which of the following substances will have hydrogen bonds between molecules?
a) (CH3)3N
b) CH3-O-CH3
c) CH3CH2-OH
d) CH3CH2-F
e) HI

** (e) can't be the answer becuz it doesn't have any Hydrogen Bonds (N,O,F)
** (a) can't be the answer becuz the N atom is by itself. H atom is attached to C atom and therefore can't bond with the N atom. Same with letter (d)

I think the answer is c... Plez correct me if I'm wrong.

Question Two:
Which of the following should have the highest boiling point?
a) CF4
b) CCl4
c) CBr4
d) CI4
e) CH4

** I think the answer if (a) becuz of the Hydrogen Bonding forces being the strongest of all forces and therefore has highest boiling point. Plez tell me know if this is the right answer or not and explain why - (if possible)

Question Three
A solution of Sucrose (sugar) in water in in equilibrium with solid sucrose. If more solid sucrose is now added, with stirring,
a) the concentration of the solution will increase
b) the concentration of the solution will decrease
c) the concentration of the solution will remain same
d) the volume of solution will increase
e) a supersaturated solution will be produced.

** (c) can't be the answer becuz something is being added so it has to change - cannot remain same. I took a guess on this one and I think its letter (a). Again please tell me if I am wrong or correct. and explain if possible.


Answers to anyone or all of these questions will be greatly appreciated. Need this 3 homework probs. done by tomorrow. Again, thanks in advance.

Regards,
Katrina

I agree that the best answer for #1 seems like C. Requirement for H bonding is that there's an electronegative atom (NOF) and a H bonded to an electronegative atom... so only answer choice C has an electronegative atom (O) and a hydrogen bonded to an electronegative atom (in the OH group)
 
And for #3, if I understood the question correctly, looking at the definition of supersaturated solution may help:

http://www.chem.purdue.edu/gchelp/gloss/supersatsoln.html

supersaturated solution: a solution that contains more solute than it would if the dissolved solute were in equilibrium with the undissolved solute
 
btw, for #2, in the given answer choices, there's no hydrogen bonding present.
 
#2 the molecules are neither polar nnor possesses hydrogen bonding... van der waal forces exist as attractive forces between them...

what does the strength of van der waal forces depend on?? from this you will be able to determine the substance with higher bp...