- #1
ashy
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Homework Statement
Gaseous helium is contained in a rigid container with a volume of V=0.5 m3, and is initially at a pressure of 500 kPa. Agitation by a stirrer transfers 250 kJ of work to the gas in an adiabatic process. Cv for the gas is constant and equal to 12.46 kJ/kmol*K. What is the final pressure of the gas?
So
At state 1: V=0.5 m3, P=500 kPa,
Process 1->2: W=-250kJ
At state 2: V=0.5 m3, P=?
cv=12.46kJ/kmol*K
Homework Equations
Energy balance for the process:
Q-W=deltaU+deltaKE+deltaPE
Q=deltaPE=deltaKE=0 so
-W=deltaU, W=-250kJ so
250kJ=deltaU.
The Attempt at a Solution
This is what I have:
250kJ=deltaU=n*deltau where u=U/n and n is the number of moles of helium.
cv=du/dT so
deltau=cv*deltaT and
250 kJ=n*cv*deltaT
I don't really know where to go with this problem to find anything to do with the pressure, the equation seems underdetermined. Help?[/B]