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 Post subject: Re: 4500 pounds of air
PostPosted: Sun Feb 09, 2014 6:14 pm 
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Joined: Thu Feb 02, 2006 11:35 pm
Posts: 3099
Location: Alberta Canada
Mr.Timberwolf wrote:
Whitewolf wrote:
Since you went with a dryer. I have to ask are you using your bottles for diving as well? Having a dryer in my opinion is quite the luxury item unless you live in a very moist climate or are using your tanks for diving.


Manitoba is quite humid in the summer time, so I am going to protect my investments with an air drier. I don't consider it a luxury item, I look at it as insurance. I have a 15 HP screw compressor in my shop and the amount of water we drain daily is stunning.


Yes will agree with the use of a screw compresor. They work great but do indeed require some form of drier inline. Lots of surface area upon the stator creating friction and heat.

Thx

_________________
May the cry of the pack be with you upon your hunt

Whitewolf


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 Post subject: Re: 4500 pounds of air
PostPosted: Sun Feb 09, 2014 10:05 pm 
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Posts: 1078
i thought carbon fiber was lighter than air? :axe:

wait, i thought a pound of air was less than a pound.... i'll google it


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 Post subject: Re: 4500 pounds of air
PostPosted: Sun Feb 09, 2014 10:15 pm 
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good news, it's lighter than i thought. you may be able to get a smaller car.

What is the weight of 1 cubic foot of air?

Asked by: Jonathan

Answer

FINAL ANSWER: 1 cubic foot of air at standard temperature and pressure assuming average composition weighs approximately 0.0807 lbs.
This one doesn't have an answer that is exact or necessarily correct as air is a composite mixture of various gases and this mixture can change due to an enormous quantity of variables. Discussing these variables and how these variables affect the air is one of the foundations of meteorology - the study of weather.

But given some data and making a few assumptions we can come to an answer that is probably pretty close.

First of all, we need to know the composition of air. What is air made of and how much is it made of. A quick internet search popped up http://www.engineeringtoolbox.com/8_212.html which gives us something to work with. (For those unfamiliar with the site's punctuation, a comma "," is used instead of a period "." a decimal delineation mark). This breakdown is actually greatly affected by where we are in the world and how far we are above sea level and other factors. We will assume average composition at sea level at 0 degrees Celsius which is known as STP or Standard Temperature and Pressure.

For reasons that should become clear a bit later, we need the volume of the various components, not the weight. This is the composition of air (as cited from the website above) by volume:

Oxygen: 20.99%
Nitrogen: 78.03%
Carbon Dioxide: 0.03%
Hydrogen: 0.00005%
Argon: 0.93%
Neon: 0.0018%
Helium: 0.0005%
Krypton: 0.0001%
Xenon: 0.000009%
There is a neat property that applies to any gas that a 22.4 liters of it at STP (standard temperature and pressure) contains 6.02214199 x10^23 molecules of said gas. This amount (Avogadro's number) is called a mole. So another way to say this is that a singe mole of gas at STP will fill 22.4 liters.

The special thing about a mole is that a if we have a molecule, we can find that molecule's molecular weight (from a periodic table) and that's how many grams a mole of the molecule would weigh. For instance, if we were to look up iron (Fe) on a periodic table, we find that its atomic weight is 55.845. A mole of iron is therefore 55.845 grams.

Quick conversion of 1 cubic foot to liters gives us 28.32 liters. Going back we can take this number to find that 28.32 liters of gas at STP is going to be 1.26414494 moles of air. Great, we can now determine how many moles of each particular substance we have from the percentage composition of air. These are the results (and the molecular symbol for each):

Oxygen (O2): 0.2653 moles
Nitrogen (N2): 0.9864 moles
Carbon Dioxide (CO2): 0.0003792 moles
Hydrogen (H2): 0.0000006321 moles
Argon (Ar): 0.01176 moles
Neon (Ne): 0.00002275 moles
Helium (He): 0.000006321 moles
Krypton (Kr): 0.000001264 moles
Xenon (Xe): 0.0000001138 moles
By looking on the periodic table for the atomic weight of constituent atoms in the above molecules (for instance CO2 we would get the weight for C and add to it twice the weight of O) and multiplying by the number of moles we have of these substances, we will get the following weights for the substances:

Note: After rounding errors and such, our current accuracy is such that anything less than 0.01g is insignificant and I have left those numbers out.

Oxygen: 8.49g
Nitrogen: 27.63g
Carbon Dioxide: 0.02g
Argon: 0.47g
Adding these numbers together (remember the rest was insignificant) we get 36.61g. Converting to pounds (since the question was in English units I assume the answer is desired in English units) we get 0.0807 lbs.

FINAL ANSWER: 1 cubic foot of air at standard temperature and pressure assuming average composition weighs approximately 0.0807 lbs


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 Post subject: Re: 4500 pounds of air
PostPosted: Sun Feb 09, 2014 11:09 pm 
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Joined: Wed Feb 17, 2010 6:04 pm
Posts: 841
Location: Nova Scotia
peterdulux wrote:
FINAL ANSWER: 1 cubic foot of air at standard temperature and pressure assuming average composition weighs approximately 0.0807 lbs


Does that mean that the air in a 71 cubic foot tank would weigh 0.0807 x 71 = 5.73 pounds?


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 Post subject: Re: 4500 pounds of air
PostPosted: Sun Feb 09, 2014 11:53 pm 
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I did not write that, copy and paste from google. I think once the 4500 psi is in a carbon tank, it's lighter than air. :axe:


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 Post subject: Re: 4500 pounds of air
PostPosted: Thu Aug 08, 2019 7:45 pm 
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Joined: Sun Aug 29, 2010 7:59 pm
Posts: 105
Location: Vancouver Island, BC
joe hickey wrote:
Pickup a used armored truck. also serves as a back stop. Say that,s not a bad idea, armored glass back stop with a slo mo camera behind the glass. Would make for some interesting video.


How about... watching it from behind the armoured glass back-stop? Trust YouTube to step it up... https://youtu.be/9L5DX8eJT-Q


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 Post subject: Re: 4500 pounds of air
PostPosted: Fri Aug 09, 2019 5:56 am 
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Joined: Thu May 07, 2015 8:30 pm
Posts: 1188
Location: Eastern Townships
cisco wrote:
joe hickey wrote:
Pickup a used armored truck. also serves as a back stop. Say that,s not a bad idea, armored glass back stop with a slo mo camera behind the glass. Would make for some interesting video.


How about... watching it from behind the armoured glass back-stop? Trust YouTube to step it up... https://youtu.be/9L5DX8eJT-Q


Interesting video, but stupid behavior. I just hope nobody will try to ''push the limits''.


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