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Q: oxygen gas: polar or non-polar? ( Answered 5 out of 5 stars,   2 Comments )
Question  
Subject: oxygen gas: polar or non-polar?
Category: Science > Chemistry
Asked by: tc_topcat-ga
List Price: $25.00
Posted: 13 Oct 2004 14:04 PDT
Expires: 12 Nov 2004 13:04 PST
Question ID: 414404
Fish suck oxygen gas dissolved in water through their gills; since
oxygen gas dissolves in a polar substance like water, oxygen gas is
polar (like dissovles like). But Lewis structures for oxygen gas show
non-polar (non-resonant) double bond structures. Please give a
detailed explanation of this apparent contradiction. Thanks
Answer  
Subject: Re: oxygen gas: polar or non-polar?
Answered By: livioflores-ga on 14 Oct 2004 09:47 PDT
Rated:5 out of 5 stars
 
Hi tc_topcat!!


Polar gases dissolve in water easily like polar liquids do, non-polar
gases which dissolve in water do it so by two ways:
 reacting to form polar products (CO2) or 
 by dipole-induced dipole interactions (O2).
The oxygen molecule O2 cross the air/water interface in a slow
process. The speed of the dissolution process depends on whether the
water is still or running, how much surface is in contact with the
air, what is dissolved in the water, and whether any films (like soap,
or oil ,etc.) are floating on the surface. Once the oxygen crosses the
air/water interface, it is caged by water molecules by weak dipole
induced forces:
"How oxygen dissolves: 
Water, as a polar molecule, induces an accumulation of electron
density (dipole moment) at one end of non-polar gas molecules such as
oxygen (O2 ) and carbon dioxide (CO2 ). ... The electron cloud of O2
is normally distributed symmetrically between the bonded O2 atoms.
When the negative end of the H2O molecule approaches the oxygen
molecule, the electron cloud of the O2 moves away to reduce the
negative-to-negative repulsion. A dipole (a molecule with positive and
negative charges separated by a distance) results in the nonpolar O2
molecule and causes O2 and H2O to become weakly attracted to each
other. This intermolecular attraction between the oppositely charged
poles of nearby molecules is termed a dipole-dipole force. The
creation of these forces explains the mechanism by which gases
dissolve in water."
From "The Chemistry of Oxygen Solubility Reading" at Water on the Web site:
http://waterontheweb.org/curricula/bs/student/oxygen/reading.html


At the above reference you will find additional info, so I suggest you
to visit that page.
Water on the Web also brings animations that help to understand the
oxygen solubility in water. The animations require the Flash plug-in.
If you are not able to view the animations, please download the
plug-in at:
http://www.macromedia.com/shockwave/download/.

"Induced Dipoles" animation:
http://waterontheweb.org/curricula/bs/student/oxygen/shock2.html

"Oxygen Solubility: Henry's Law" animation:
http://waterontheweb.org/curricula/bs/student/oxygen/shock1.html

Additional resources at this site can be found at PROCEDURES section
of the page "Teaching about the Chemistry of Oxygen Solubility":
http://waterontheweb.org/curricula/bs/teacher/oxygen/teaching.html


The following text give us more info about polar molecules and induced
dipoles forces:
"We can also have the attraction of a dipole for a molecule that is
ordinarily not a dipole. When a dipole approaches a nonpolar molecule,
its partial charge either attracts or repels the electrons of the
other particle.
For instance, if the negative end of the dipole approaches a nonpolar
molecule, the electrons of the nonpolar molecule are repelled by the
negative charge. The electron cloud of the nonpolar molecule is
distorted by bulging away from the approaching dipole as shown in
Figure 14-3.
As a result, the nonpolar molecule is itself transformed into a
dipole. We say it has become an induced dipole. Since it is now a
dipole, it can be attracted to the permanent dipole.
Interactions such as these are called dipole-induced dipole forces. An
example of this force occurs in a water solution of iodine. The I2
molecules are nonpolar while the water molecules are highly polar. The
case of two nonpolar molecules being attracted must also be taken into
account.
For instance, there must be some force between hydrogen molecules;
otherwise it would be impossible to form liquid hydrogen. Consider a
hydrogen molecule with its molecular orbital including both nuclei. We
know intuitively that the electrons occupying that orbital must have a
specific location. If they are both away from one end of the molecule
for an instant, then the nucleus is exposed for a short time.
That end of the molecule has a partial positive charge for an instant;
a temporary dipole is set up. For that time, the temporary dipole can
induce a dipole in the molecule next to it and an attractive force
results as shown in Figure 14-4. The forces generated in this way are
called dispersion forces."
From "Polar Molecules" at San Lorenzo Valley High School site:
I suggest to visit this page to see the figures and further reading.
http://cougar.slvhs.slv.k12.ca.us/~pboomer/chemtextbook/cch14.html


Additional references related are:

"Intermolecular Forces and Solutions":
http://employees.csbsju.edu/hjakubowski/classes/Chem%20of%20Disease/IMF_Solutions/olIMF_solutions.htm

"Intramolecular Forces (intra means within)":
http://jhss.wrdsb.on.ca/library/html/assignments/science/bond2.htm

"Definition of London forces":
http://www.wordiq.com/definition/London_forces

"Henry's Law and the Solubility of Gases":
http://www.psigate.ac.uk/newsite/reference/plambeck/chem2/p01182.htm

"Why does the solubility of gases usually increase as temperature goes down?"
http://antoine.frostburg.edu/chem/senese/101/solutions/faq/temperature-gas-solubility.shtml

"How can I predict oxygen solubility in water?"
http://antoine.frostburg.edu/chem/senese/101/solutions/faq/predicting-DO.shtml


------------------------------------------------------------

Search strategy:
"how oxygen" dissolved
gas dissolved water
dipole force gas dissolved
Induced Dipoles water oxygen
"induced dipole" oxygen water solution

-------------------------------------------------------------

I hope that this helps you. Plesar use the clarification feature to
request clarifications if you find something unclear or incomplete
before rate this answer. I will gladly give you further assistance on
this.


Best regards.
livioflores-ga

Request for Answer Clarification by tc_topcat-ga on 14 Oct 2004 14:57 PDT
Thanks for the impressive array of information assembled to answer my
question. Appreciate the help. One follow-up for a question that
wasn't addressed: are there alternate, polar-covalent forms of O2
bonding? I recall something about oxygen gas being an exception to the
octet rule with each oxygen atom in an O2 pair being "happy" with
seven electrons, rather than eight. This would provide an alternate
take on why O2 dissolves in water since, with an incomplete octet, the
diatomic molecule would now be polar. Do you have any info on this
aspect?

Thanks again for your excellent help.

Tom Clements

Clarification of Answer by livioflores-ga on 14 Oct 2004 20:39 PDT
Hi!!

First of all thank you for the good rating and the generous tip.


Regarding to your last question unfortunately I did not find evidence
or references of such incomplete octet bonding in the oxygen molecule.
And I have not enough chemical skills to discuse based on my own
knowledge. So I give you some references that I think could bring you
additional resources on Oxygen molecule bonding:
"Bonding":
See the Covalent Bonding section.
http://v.d.singleton.home.att.net/genchem/bonding.htm
http://v.d.singleton.home.att.net/genchem/bonding.htm#covalent

"Molecular Orbitals: Diatomic Molecules With Identical Atoms":
http://www.psigate.ac.uk/newsite/reference/plambeck/chem1/p02212.htm

"Molecular Orbital Theory":
http://chem.ufl.edu/~chm2040/Notes/Chapter_12/theory.html

"Valence Bond and Molecular Orbital Models":
See the figure 35 and the related text.
http://wulfenite.fandm.edu/Intro_to_Chem/valence_bond_and_mo_models.htm

"Molecular Orbital Theory":
http://chem.ufl.edu/~chm2040/Notes/Chapter_12/theory.html

"Why is Ozone Such a Strong Oxidizing Agent?"
http://www.chemistry.wustl.edu/~edudev/LabTutorials/AirQuality/Oxidizer.htm


I also add the following article that give additional info related to
the solubility of the oxygen in water:
"Why does the solubility of oxygen decrease when the salinity of the
water increases?":
From Singapore Science Centre.
http://www.science.edu.sg/ssc/detailed.jsp?artid=5686&type=6&root=5&parent=5&cat=60


I hope that this helps you at least a little.

Regards.
livioflores-ga
tc_topcat-ga rated this answer:5 out of 5 stars and gave an additional tip of: $5.00
excellent response

Comments  
Subject: Re: oxygen gas: polar or non-polar?
From: gjking-ga on 13 Oct 2004 18:04 PDT
 
Oxygen gas is nonpolar.  I believe (I'm guessing) the reason it is
soluble in a polar substance like water is because the water molecules
can temporarily induce dipoles in the O2 molecules, resulting in weak
attractive forces.  However, oxygen is significantly less soluble in
water than a polar substance like CO2 or NH3, as the
like-dissolves-like rule suggests.
Subject: Re: oxygen gas: polar or non-polar?
From: acrh2-ga on 13 Oct 2004 20:22 PDT
 
O2 is nonpolar.  But there's no contradiction with the "like dissolves
like" rule: solubility of oxygen in most nonpolar solvents is much
higher than in water.

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