chstudent24
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General Chemistry II
Hey everyone. I took chem 1 my freshman year and did alright. I attempted to take chem 2 a few times and had to drop. Now its 4 years later, I have a
job and I've completed everything in my degree but this last annoying course. Since I'm working, I'm taking this class via correspondence, so I can
take my time and really understand things. I'll post my questions/confusions here since this subject really seems to confuse me.
The first question
What kind of intermolecular attractive force is shown in each of the following cases? (They show little circle diagram shapes with 5 dots connection
each)
a. HF....HF
b. FF.....FF
c. Na+.....OH2
d. SO2.....SO2
I'm really stumped on how to even begin.
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entropy51
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We charge $50 per hour for chemistry tutoring and homework help. Please enter your PayPal account number.
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JohnWW
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I would say:
(a) hydrogen bonding;
(b) Van-Der-Waals intermolecular forces (which are the weakest of the intermolecular forces other than gravitation);
(c) solvation of a cation due to electrostatic force arising from the polarity of the O-H covalent bonds with a slight negative charge on the O and
the slight degree of ionization of water (and involving also weak dative bonding of electron pairs on the oxygens to the empty 3s and 3p orbitals on
Na+, but only a very few salts with hydrated Na+ cations can be isolated as solids by crystallization at low temperatures, such as natron or washing
soda, Na2CO3.10H2O, and Glauber's salt or thenardite, Na2SO4.10H2O); and
(d) partly the same as in (b) plus substantial contribution from intermolecular dipole electrostatic attraction as in (c) due to the polarity of the
S=O bonds, with the Os being slightly negative and the S being slightly positive.
None of the intermolecular bonds are actual chemical bonds.
[Edited on 9-7-09 by JohnWW]
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1281371269
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Entropy that's not strictly true - help will be given for free but you have to pose the questions in more subtle ways. Try calling the thread
'Intermolecular Forces' and mention a failed practical somewhere in your post. You'll get loads of replies.
The answers 'ionic' and 'covalent' presumably are simpler than required here?
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entropy51
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I think so. In solution and solids you have attractive forces that are not chemical bonds, which is what you have guessed. More likely the three
kinds of van der waals forces: (1) dipole-dipole, (2) dipole-induced dipole, and (3) induced dipole-induced dipole.
But charging for tutoring might buy Polverone a better web hosting service.
A better first post might have started off "my textbook describes the types of intermolecular forces as blah blah blah" just to show that you had at
least read the book before asking someone else to do your homework.
[Edited on 8-7-2009 by entropy51]
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1281371269
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But it might reduce my lab budget even further!
'Van der Waals forces include attractions between atoms, molecules, and surfaces. They differ from covalent and ionic bonding in that they are caused
by correlations in the fluctuating polarizations of nearby particles (a consequence of quantum dynamics).'
I'm trying to understand this, however...
It says though that they mainly refer to organics, whereas the bonds given in the first post seem to be inorganic?
[Edited on 8-7-2009 by Mossydie]
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DJF90
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Van der waals forces act on every molecule, whether they be organic or inorganic. The force arrises due to momentary unequal elecron density in the
bond (as the electons are orbiting the nuclei - you can't expect them to sit in equally between the two nuclei (only for a small proportion of time
) causing a momentary dipole. This can then interact with another momentary
dipole on an adjacent molecule, induce a dipole on an adjacent molecule, or interact with a permanent dipole on an adjacent molecule.
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chstudent24
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Thanks for the replies everyone. I apologize for not doing a great job on my first post. I'm not here to steal answers for homework. I don't care
about chemistry, but I accept the fact that i have to take this course, so I will put forth the work. I don't need any answer responses, i find a
question or something leading me to the answer more helpful.
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vulture
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| Quote: |
I don't care about chemistry, but I accept the fact that i have to take this course, so I will put forth the work. |
I appreciate your honesty. However, let's perform a little thought experiment. Assume someone comes to a forum which is about your passion, asks a
question which can be deduced with some elbow grease and then says they don't really care about the subject.
Would you be inclined to offer this person your assistance whilst withholding your scorn?
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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The_Davster
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Thread Moved
12-7-2009 at 15:37 |
chstudent24
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Quote: Originally posted by vulture  | | Quote: |
I don't care about chemistry, but I accept the fact that i have to take this course, so I will put forth the work. |
I appreciate your honesty. However, let's perform a little thought experiment. Assume someone comes to a forum which is about your passion, asks a
question which can be deduced with some elbow grease and then says they don't really care about the subject.
Would you be inclined to offer this person your assistance whilst withholding your scorn? |
I'm just being purely honest with the situation this subject frustrates me a lot, i'm putting this out there since i'm always open to change. I'm
hoping the passion of you guys will rub off on me.
But whatever the case i'll put more elbow grease into it before posting again. I'll post up my work/attempt and thought process which will be more
helpful to me and also the people willing to help.
Cheers
[Edited on 13-7-2009 by chstudent24]
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chstudent24
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Ok so here is my updated thought process please let me know if I'm wrong in my thinking.
a. HF....HF
Ok so this is a Hydrogen bond since they exist when H is covalently bonded to N, O, or F which we have here. And since F has a very high EN
this makes it very polar which hydrogen bonds are
b. FF.....FF
This is a London Dispersion since the F2 and F2 cancel out the EN of each other creating a non polar molecule which defines a London
Dispersion force
c. Na+.....OH2
This is an ionic bond because it first invovles a bond between a metal and non metal and is formed by 2 oppositley charged ions.
d. SO2.....SO2
Dipole-Dipole because this force requires 2 polar molecules. The polarity can be easily determined from the bent shape of these
molecules
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chstudent24
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Viscosity (double checking understanding)
Is the viscosity of glycerol larger or smaller than that of 1-propanol?
Viscosity= The resistance of a liquid to flow. From reading around I found that Glycerol is described as a viscous substance. So I'd assume the
viscosity of glycerol would larger than that of 1-propanol. The book says viscosity is found via timing a flow through a tube or measuring the rate at
which a steal sphere falls through a liquid. These test make perfect sense to me, but how can I determine this on my own (like during a test) with
just having the name of a substance like i did in this question?
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12AX7
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You use a viscometer. There are lots of methods, but keep in mind that, fluid flow being what it is, there are lots of ways to measure -- it's not as
simple a standard as, say, measuring the density of a solid block of matter. It also depends on the shear rate, to varying amounts, with varying
materials (see: rheology). Wikipedia has a list of common viscometer types.
In your last sentence, are you asking for a table of viscosities of common materials (such as glycerol)? I imagine such a thing exists, have you
tried searching?
Tim
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kclo4
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Perhaps they are expecting one to expect the viscosity by the structure of the molecule? Gylcerol while having three carbon atoms like propanol, it
has three hydroxyl groups, while propanol has only one. I'd imagine hydrogen bonds might play a roll in viscosity?
It doesn't seem like the questions really wants a number sort of answer, but it may.
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chstudent24
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Intermoleculer Forces (again)
What types of intermolecular force is (are) common to a) Xe and methanol (CH3OH), b) CH3OH and acetonitrile (CH3CN), c) NH3 and HF?
XE-CH3OH
London-molecule isn't non polar so can't be
Dipole-Dipole-moleclue is polar so dipole-dipole
Hydrogen-no N, O, F or C on the left so can't be
Ionic- Can't be because this isnt between a metal and nonmetal
CH3OH-CH3CN
London-the EN is very close i want to say this is a london
Dipole-Dipole-EN come close , the math would say its a close polar molecule so i'd say Dipole-Dipole
Hydrogen-I see H bonded to O and C but not sure if i'm making a mistake here to label this a hydrogen bond
Ionic- Can't be because this isn't between a metal and nonmetal
NH3-HF
London-isn't polar so can't be
Dipole-Dipole-is polar so does have this but hydrogen since of very high polarity
Hydrogen- H is bonded to an N and F so i'd assume this is a hydrogen bond
Ionic- Can't be because this isn't between a metal and nonmetal
not exactly sure if the question was asking which do they all have in common jointly, if it was I would say Dipole-Dipole from what i wrote above.
Please correct any flaws with my reasoning!
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chstudent24
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thank you for the responses. After looking back at the question I figure it was trying to have me focus on the shape of the molecule to identify the
viscosity.
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The_Davster
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Threads Merged
13-7-2009 at 06:16 |
The_Davster
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Threads Merged
13-7-2009 at 06:16 |
vulture
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This seems to be a trick question. Ammonia and hydrogen fluoride will form ammonium fluoride, which is a salt. That should give you a clue tot the
interaction.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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