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