 #1
Astrocyte
 12
 2
 Homework Statement:

What is the change in entropy of van der Waals gas in free expansion?
Free expansion from V to 2V
 Relevant Equations:
 (p+aN^2/V^2)(VNb)=NkT
Previous of this problem, there was another problem. that is "What is the change in Temperature of van der Waals gas in free expansion?".
I got them.
It was
C_V dT= aN^2/V^2 dV
Then, I got
T=T0aN^2/2VC_V
So i knew that the Temperature is decreased by free expansion in adiabatic process.
Then I calculated some about the change of entropy.
And I notice that this result says "entropy can be decreased for Free expansion of Waals gas.
What did i do wrong for this calculation?
I got them.
It was
C_V dT= aN^2/V^2 dV
Then, I got
T=T0aN^2/2VC_V
So i knew that the Temperature is decreased by free expansion in adiabatic process.
Then I calculated some about the change of entropy.
And I notice that this result says "entropy can be decreased for Free expansion of Waals gas.
What did i do wrong for this calculation?
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