Temperature increase in a fixed volume when adding mass

[david316]

Hello,

I'm interested to know if that in a fixed insulated volume (e.g. 500ml), at some temperature (e.g. 293K) and pressure (e.g. 1 atmosphere), and you increase the pressure by a specific amount by pumping more gas (e.g. air at 293K) into the volume can you work out the expected increase in temperature. As far as I can tell, you can't use adiabatic compression as you are adding mass to the system. The ideal gas equation won't work because the final number of moles and temperature are unknown. Is there are way to solve this?

Thanks a lot

 

[russ_watters]

If you add "a specific amount" of additional gas, then isn't the final number of moles known?

 

[david316]

Sorry, its not worded very well. I increased the the pressure by a specific amount (e.g. 20 cmH2O) not the number of moles. I don't know how a increase in pressure translates to a number of moles as the temperature can change as well.

 

[Chestermiller]

Sorry, its not worded very well. I increased the the pressure by a specific amount (e.g. 20 cmH2O) not the number of moles. I don't know how a increase in pressure translates to a number of moles as the temperature can change as well.

Are you familiar with the open system version of the first law of thermodynamics?

Chet

 

[david316]

I am now. Thanks.