
#1
Oct107, 06:28 AM

P: 25

Hi
I have an ongoing dispute with my mate on this one, please help to clarify this before I open up a can of whoop *** on that sorry mofo. 300 litres of air are compressed into a 3 litre tank. What is the heat capacity of this air? Thanks in advance. 



#3
Oct207, 03:51 AM

P: 25

The Cp J mol is 29.19. But because I ask for constant volume, it is definately lower then this. This is what I think. I can find no references to constant volume anywhere and unfortunately I have no teacher to ask as I study archaeology, not physics.
Do you have the answer? Thanks in advance. 



#4
Oct207, 09:53 AM

Sci Advisor
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P: 6,576

Heat Capacity of Air at Constant VolumeAM 



#5
Oct207, 10:54 AM

P: 25

Hi,
Thanks for the reply. Is 1.4 per gram or mol? Also, How can you measure a gram of gas and how much is 1 mol? Cheers. 



#6
Oct207, 11:03 AM

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P: 8,961

1.4 is a ratio ( actually nearer 1.3 for dry air at room temp)
see http://en.wikipedia.org/wiki/Heat_capacity_ratio 1 mol of air is roughly 30g or 22.4litres at STP ( 0deg C 1 atm) 



#7
Oct207, 10:30 PM

P: 3,408

Is heat capacity independent of volume for an ideal gas?
Stupid question  gas performs work while being compressed. 



#8
Oct307, 08:30 AM

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P: 8,961

For an ideal gas heat capcity just depends on the amount (number of moles) present and the number of vibration states of the molecular.
For a real gas it also depends on the pressure because the molecules close to each other change the vibration state/bond energy. 



#9
Oct307, 11:19 AM

P: 3,408

In a modification of the "ideal gas" law, I seem to recall an equation with correction terms for the volume and pressure, respectively. Has anyone run across this?




#10
Oct807, 08:36 AM

P: 25

Hi,
This ratio of 1.4, does this just mean that you divide the constant pressure capacity (1.020J/g) by 1.4? 



#11
Oct807, 12:53 PM

Sci Advisor
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P: 6,576

AM 


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