- #1

Astrocyte

- 13

- 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)(V-Nb)=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=T0-aN^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=T0-aN^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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