- #1
Northbysouth
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Homework Statement
A piston-cylinder assembly contains air, initially at 2 bar, 300 K, and a volume of 2m3. The air undergoes a process to a state where it pressure is 1 bar, during which the pressure-volume relationship is pv = constant. Assuming idea gas behavior for the air, determine the mass of the air, in kg and the work and heat transfer, each in kJ
Homework Equations
pv-nrt
W = ∫p dv
The Attempt at a Solution
I found the constant C to be:
pivi = (200,000 Pa)(2m3)
C = 400,000 Pam3
vf = C/pf
Hence vf = 400,000 Pa m3/100,000 Pa
vf = 4m3
W = ∫P dv = ∫24C/v dv
W = 277258.9 kJ
Mass of air:
pv =nrt
n = (200,000 Pa)(2m3)/(8.314 J/K mol)(300K)
n = 160.372 Pa m3mol/J
I'm a little fuzzy on moles and such, but unless I'm much mistaken, I should be able to find the mass of the air by dividing by Avogadro number, right?
After this, I can calculate the heat transfer with Q = mcΔT in which I can find the ΔT with the relationship:
pivi/Ti = pfvf/Tf
Am I making sense?