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(Kelly E Jones) wrote in news:c950es$71o$1
@news01.intel.com:

In article ,
Salty Thumb wrote:

If you work out Van der Waal's equation:

http://chemed.chem.purdue.edu/genche...eviation5.html

at 1 atm and 20C, I get

02 1 mol / 2.74 L
N2 1 mol / 2.74 L
CO 1 mol / 2.73 L
CO2 1 mol / 2.49 L

making CO2 the most dense (unless I solved the equation wrong which is
entirely likely: v^3 - bv^2 = av - ab - RT = 0).

The difference between CO and O2 doesn't seem remarkable enough to be
significant, but I guess at greater concentrations it'd be workable. I
think you'd be more likely to kill yourself than the rat, though.

[I'm not a chemist or physicist, so all this could a bunch of hokey.]

Well, the way you're using it IS a bunch of hokey. You've calculated
molar density, not mass density. That's equivalent to saying 100
bowling balls takes up more space than 100 baseballs, since a 'mole'
is just a fixed number of atoms (somewhat more than a 'sh*tload'). It
says nothing about which is 'heavier'. You're better off just
ignoring molar density (as the previous poster did ) since, as you
note, they're all pretty close, and just going with the mass density.
CO2 is denser than 'air', and CO is slightly lighter.

Kelly


100 bowling balls do take up more space than 100 baseballs, and the size
of the molecules is something the Van der Waals equation takes into
account that the Ideal Gas equation does not. (at STP the variation is
not very significant, but if you use the ideal gas equation, obviously
you get the same answer for every compound). [for people who don't
remember their chemistry a mole is Avogadro's number of particles ~= 6.02
x 10^23]

If you take the molar density and multiply by the molecular weight, you
get the mass density.
02 1 mol / 2.74 L = 11.7 g/L
N2 1 mol / 2.74 L = 10.2 g/L
CO 1 mol / 2.73 L = 10.3 g/L
CO2 1 mol / 2.49 L = 17.7 g/L

Assuming the numbers are right, oxygen has more mass density than carbon
monoxide (but slightly less particle density). For purposes of
asphixation, the CO vs O2 comparison is what matters.

I still can't work out how mass density is relevant when talking about
gases or how adding atomic weights can give a correct indication of
density or buoyancy. It would be akin to saying water floats on oil
(obviously it doesn't), because water (1 + 1 + 16 = 18) is lighter than
oil (say minimum of 2 H and 2 C = 26). To me it makes more sense (when
talking about gases at least) to talk about particle density, but I'm not
convinced particle density is the solution, either.