Tom Quackenbush wrote in
:

Not Me wrote:
"Tom Quackenbush"

| I should also mention that CO is heavier than O2 so the
| atmosphere
| at the bottom of the rat hole will be have increasingly
| concentrated CO levels. If all else fails the critter will have
| one h*ll of a head ache.
|
| C = 12, O = 16, N = 14
|
| CO = 28, O2 = 32, N2 = 28

The real world physics/dynamics is not quite that simple but
sufficient to say CO is heavier than air and will settle to the lowest
level i.e. the bottom of the rat hole.

Are you sure you're not thinking of CO2?

Carbon monoxide is obviously lighter than air (but not by much). If
you don't believe me, Google for "carbon monoxide lighter air".

R,
Tom Q.

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.]
(rec.gardens)

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

Xref: kermit rec.gardens:280489 misc.rural:132645 misc.consumers.house:106972 alt.home.repair:481262

(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.

In article ,
Salty Thumb wrote:

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

True!


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.

Not really... O2 and N2 don't separate out - they form, effectively, a
'solution', so the density of 02 is not really relevant. It's the
density of 'air' which matters, which is between the density of air
and nitrogen (and closer to nitrogen).

I still can't work out how mass density is relevant when talking about
gases

Because mass density, coupled with gravity, is what causes bouyancy.

or how adding atomic weights can give a correct indication of
density or buoyancy.

Because for most gases (at fixed temperature and pressure), the molar
volume (molar density) is roughly constant, thus the molecular weight
is a good indicator of the mass density, which determines bouyancy.

If we say that a mole of any gas occupies roughly 24 liters at STP,
and a mole of gas weighs it's molecular weight in grams, then the
density of any gas is proportional to it's molecular weight. The
density of CO2 is thus about 44 grams per 24 liters.

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).

No, gases and liquids are vastly different phases. The molar volume
of most gases (at STP) is roughly the same; the molar volume of
liquids can be orders of magnitude in difference.


To me it makes more sense (when
talking about gases at least) to talk about particle density

Nope, not at all. Gravity doesn't care at all about particles, it
only cares about mass...

Kelly

That makes sense, thanks for the explanation.

(Kelly E Jones) wrote in
:

In article ,
Salty Thumb wrote:

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

True!


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.

Not really... O2 and N2 don't separate out - they form, effectively, a
'solution', so the density of 02 is not really relevant. It's the
density of 'air' which matters, which is between the density of air
and nitrogen (and closer to nitrogen).

I still can't work out how mass density is relevant when talking about
gases

Because mass density, coupled with gravity, is what causes bouyancy.

or how adding atomic weights can give a correct indication of
density or buoyancy.

Because for most gases (at fixed temperature and pressure), the molar
volume (molar density) is roughly constant, thus the molecular weight
is a good indicator of the mass density, which determines bouyancy.

If we say that a mole of any gas occupies roughly 24 liters at STP,
and a mole of gas weighs it's molecular weight in grams, then the
density of any gas is proportional to it's molecular weight. The
density of CO2 is thus about 44 grams per 24 liters.

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).

No, gases and liquids are vastly different phases. The molar volume
of most gases (at STP) is roughly the same; the molar volume of
liquids can be orders of magnitude in difference.


To me it makes more sense (when talking about gases at least) to
talk about particle density

Nope, not at all. Gravity doesn't care at all about particles, it
only cares about mass...

Kelly

Salty Thumb wrote:
snip

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.]
(rec.gardens)

I think there's something wrong with those numbers. 1 mole of
(ideal) gas occupies 22.4 L @ STP. Your numbers should vary slightly.

Kelly's already done a bang-up job of explaining why you need to
bring mass back into the picture.

R,
Tom Q.

Salty Thumb wrote:
snip
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

As I mentioned in my previous post, I think those volume figures are
a little off.

According to my handy-dandy Pocket Ref, here are the densities (@
STP):

O2 1.4290 g/L
N2 1.2506 g/L
CO 1.2500 g/L
CO2 1.9770 g/L
Air 1.2928 g/L

Just as a sanity check, I multiplied each one of those figures by
22.4 to make sure that the product was close to the molecular mass
(they are).

R,
Tom Q.

On Thu, 27 May 2004 20:21:40 -0400, Tom Quackenbush wrote:
Kelly's already done a bang-up job of explaining why you need to
bring mass back into the picture.

Um. Hate to be practical and everything here, but if you're forcing
a gas into the gopher hole, the density doesn't matter; it's not going
there by gravity, it's going there by pressure. You could force
helium down there and it'd go down rather than up, density and
molecular mass notwithstanding.

Kelly E Jones wrote:
Salty Thumb wrote:
snip

or how adding atomic weights can give a correct indication of
density or buoyancy.

Because for most gases (at fixed temperature and pressure), the molar
volume (molar density) is roughly constant, thus the molecular weight
is a good indicator of the mass density, which determines bouyancy.

If we say that a mole of any gas occupies roughly 24 liters at STP,
and a mole of gas weighs it's molecular weight in grams, then the
density of any gas is proportional to it's molecular weight. The
density of CO2 is thus about 44 grams per 24 liters.

snip

This property can come in very handy, as long as you know a few
key atomic weights. Say, for instance, that you're stuck in a boring
class or lecture. No problem. Whip out your pencil and notepad and
calculate how much H2 it would take to float your neighbor's cat into
the stratosphere. Next, calculate how much He to do the same thing.
Look up at the lecturer from time to time, appearing thoughtful. He or
she will be impressed that you're taking more notes than any one else
in the room.

The above is a purely hypothetical scenario. g

R,
Tom Q.

In article ,
Tom Quackenbush wrote:

Just as a sanity check, I multiplied each one of those figures by
22.4 to make sure that the product was close to the molecular mass
(they are).

Erg. Now you've made me realize that mis-remembered that the molar
volume of a gas is 22.4, not 24 as I stated in my previous posts.
Been a long time since college...

Kelly

Xref: kermit rec.gardens:280549 misc.rural:132716 misc.consumers.house:107006 alt.home.repair:481376

Tom Quackenbush wrote in
:

Salty Thumb wrote:
snip
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

As I mentioned in my previous post, I think those volume figures are
a little off.

According to my handy-dandy Pocket Ref, here are the densities (@
STP):

O2 1.4290 g/L
N2 1.2506 g/L
CO 1.2500 g/L
CO2 1.9770 g/L
Air 1.2928 g/L

Ha, thanks, but mine were way off. This is why I am not a chemist (or
mathematician). The correct equation is probably: v^3 - (b + RT) v^2 + a
V - ab = 0 (forgot to multiply RT by v^2 last time)

which gives
CO 1.168 g/L at 20C, 1 atm
CO 1.253 g/L at STP (using 28 for mass)

Close enough to the value you reported.

Calculations for other compounds are an exercise left to the reader

Xref: kermit rec.gardens:280552 misc.rural:132718 misc.consumers.house:107009 alt.home.repair:481378

(Kelly E Jones) wrote in news:c963nr$p9u$1
@news01.intel.com:

In article ,
Tom Quackenbush wrote:

Just as a sanity check, I multiplied each one of those figures by
22.4 to make sure that the product was close to the molecular mass
(they are).

Erg. Now you've made me realize that mis-remembered that the molar
volume of a gas is 22.4, not 24 as I stated in my previous posts.
Been a long time since college...

Kelly


The volume is around 24.04 L/mol at 20C, 1 atm (which is the temp I
calculated at) and 22.4 L/mol at STP.