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rodder-robert
10-06-2006, 04:46 PM
how much volume will a 12 gram co2 fill and still maintain 800 psi?
neppo1345
10-06-2006, 05:27 PM
PV = nRT
MoeMag
10-07-2006, 01:12 AM
Good thinking, but its not that simple. you have to deal with the fact that it is stored in a liquid state. CO2 has a vapor pressure of about 800-850psi... so as long as there is liquid within a contained volume you should have appx. 800 psi.
I am actually curious about this too...
I think the question is actually, how much gas does 12 grams of liquid co2 convert into?
anyone care to answer that? ...im working on it too.
MantisMag
10-07-2006, 07:39 AM
12g of gas. :p
jenarelJAM
10-07-2006, 01:50 PM
lol mantis... you didn't understand what he just said.
co2 is stored as a liquid at ~800 psi
When it comes out of your gun, it's a gas. At about 800 psi, gas co2 compresses into liquid form, where it is denser, but retains the same pressure(about). As liquid turns to gas, it expands, but as long as there is a little liquid left in the tank, trying to expand, it stays at about 800 psi.

He was asking how much volume of 800 psi gas a 12g would put out.

Edit- and maybe I didn't understand what you said, if you referred to 12g of gas as the mass.
slade
10-08-2006, 09:41 AM
well, if 12 grams is an accurate measurement, you could find the molecular weight of CO2 (its 44), calculate the moles of gas that would give you, and then plug that into pv=nrt. you have n, r is a constant, you can estimate t, you know p, and that would give you v.

just remember, 1 ATM = 14.7 PSI.

damn, its funny how much you forget in a few months, last year i would have had the answer before i could finish typing that.
bjjb99
10-08-2006, 09:54 PM
At 800 psi on an average 25 degree C day, CO2 will exist purely as a gas. 12 grams of CO2 gas at 800 psi (relative to atmospheric pressure, 814.7 psi absolute pressure) and 25 degrees C will occupy approximately 7.4 cubic inches. That's a cube 1.95 inches on a side, or a sphere 2.4 inches in diameter.

BJJB
jenarelJAM
10-09-2006, 02:06 PM
Except that at higher pressures, the melting/freezing curve shows it so you have liquid co2 at room temperature. I thought...

You are going to get alot of volume out of the liquid changing to a gas, and more volume out of the gas depressurizing.
slade
10-09-2006, 02:09 PM
oh, i almost forgot. also, remember that PV=NRT is for an ideal gas. CO2 deviates more than most from the behavior of an ideal gas, so for any calculation of high precision, you may have to take that into account.
bjjb99
10-09-2006, 02:30 PM
Except that at higher pressures, the melting/freezing curve shows it so you have liquid co2 at room temperature. I thought...

You are going to get alot of volume out of the liquid changing to a gas, and more volume out of the gas depressurizing.

The phase diagram for CO2 puts it as a gas at 800 psi and 25 degrees C, which is around room temperature.

Remember, the question is about how much volume 12 grams of CO2 occupies once it turns into a gas. 12 grams of CO2 is the mass of the CO2. It doesn't matter whether the CO2 is a solid, a liquid, or a very sparse gas to start with--it's still 12 grams.

Slade, I agree that CO2 certainly deviates from an ideal gas. For this discussion, however, I think we'll probably get fairly close (within 5 or so percent) if we treat it as if it were.

BJJB
jenarelJAM
10-09-2006, 02:33 PM
I guess I was thinking of energy then... I hate chemistry... I'm glad I took my AP test last year instead of this year... I don't want to deal with it again...
MantisMag
10-09-2006, 07:39 PM
you took AP chem? :confused:
StuDawggie
10-10-2006, 06:38 AM
Shouldn't this be moved to "Deep Blue"? There is way to much advanced level thinking here, and it's about to make by brain explode this early in the morning.
slade
10-10-2006, 12:48 PM
Shouldn't this be moved to "Deep Blue"? There is way to much advanced level thinking here, and it's about to make by brain explode this early in the morning.
advanced level thinking? this is all simple stuff.
tropical_fishy
10-10-2006, 01:32 PM
advanced level thinking? this is all simple stuff.


Most people don't know chem.

/shudder ugh, chem. I think I have a chem quiz tomorrow, come to think of it...
slade
10-10-2006, 01:35 PM
Most people don't know chem.

/shudder ugh, chem. I think I have a chem quiz tomorrow, come to think of it...
yeah, your chem teacher is evil with the meticulousness of work.

my chem teacher was just plain evil :ninja: