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Molecular radii - references

Molecular radii - references - Chemistry Forum

Molecular radii - references - Chemistry Forum. Discuss chemical reactions, chemistry.


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  #1  
Old 03-04-2004, 09:28 AM
Peter
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Default Molecular radii - references



Hey,

For research, I need molecular diameters of various molecules, but I'm
having difficulties finding them (all).
Therefore, my question is: which (hand)books are typical sources for such
information.

To illustrate which numbers I'm looking for; I did find molecular diameters
of some species - but unfortunately the paper I got them from did not
contain the original source/reference. These molecules (and corresponding
values) are:
e.g.:
H2O : 2.52 Angstrom (diameter)
CO2: 3.94 A (diameter)

Thanks!

Peter


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  #2  
Old 03-04-2004, 01:40 PM
Abdul Qat
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Default Molecular radii - references


"Peter" <[Only registered users see links. ]> wrote in message
news:c26ssb$t2e$[Only registered users see links. ].utwente.nl...
diameters

The term 'molecular radii' doesn't have a precise meaning. Perhaps you
could use the static dipole polarizability of a molecule as a measure ot
its orientationally averaged volume and from that come up with some
estimate of its 'radius'.

--
Salam,
Abdul Qat


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  #3  
Old 03-05-2004, 05:21 PM
Repeating Rifle
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Default Molecular radii - references

in article c26ssb$t2e$[Only registered users see links. ].utwente.nl, Peter at
[Only registered users see links. ] wrote on 3/4/04 1:28 AM:

A quick and dirty calculation leaves me with some doubt about the molecular
diameters. The formula weight for water is 18. Thus the number of melecules
in a cubic centimeter is approximately 6.02E23/18 = 3.34E22/cm^3. Thus, the
volume available per molecule is 3.0E-23 cm^3. If the molecule were cubic,
the length of an edge would be 3.1 angstroms. How can your 2.52 angstrom
diameter be correct?

Bill

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  #4  
Old 03-06-2004, 07:03 PM
Mark Tarka
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Default Molecular radii - references

Repeating Rifle <[Only registered users see links. ]> wrote in message news:<[Only registered users see links. ]>...

Gas phase.


Mark (Theory is gas at 0 K ... isn't it?)
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  #5  
Old 03-07-2004, 06:25 AM
Repeating Rifle
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Default Molecular radii - references

in article [Only registered users see links. ], Mark Tarka at
[Only registered users see links. ] wrote on 3/6/04 11:03 AM:


"Gas phase." is not a complete sentence. Thus, it is meaningless. If you
mean to imply that the substance is in the gas phase, then it would be less
dense than the liquid phase. that means the volume of a water molecule will
be even greater than what was quoted.

Bill

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  #6  
Old 03-07-2004, 06:52 PM
Mark Tarka
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Default Molecular radii - references

Repeating Rifle <[Only registered users see links. ]> wrote in message news:<[Only registered users see links. ]>...

Sorry. I meant "cubic gas phase", which is a complete
sentence where the subject ("it"), verb ("is"), and
introduction to the prepositional phrase ("in the"),
are all understood, as in "Who?".

I calculated 3.85 angstroms for a spherical model.
2.77 is the "hard-sphere" diameter. ~13 is estimated
from the second virial coefficient. And we know it's
less than 4 when we dry solvents using mol sieves.

Would the diameter of water be more or _less_ in the
gas phase (in a vacuum)?

I could imagine it to be effectively more as a gas
in the atmosphere due to interactions with O2 and N2.


Mark
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  #7  
Old 03-07-2004, 10:47 PM
Mark Tarka
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Default Molecular radii - references

Repeating Rifle <[Only registered users see links. ]> wrote in message news:<[Only registered users see links. ]>...

English.


Did. [Only registered users see links. ]


Nope.



Mark (> > Would the diameter of water be more or _less_ in the
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