## 9.47 isothermal, irreversible free expansion [ENDORSED]

isochoric/isometric: $\Delta V = 0$
isothermal: $\Delta T = 0$
isobaric: $\Delta P = 0$

Lindsay H 2B
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### 9.47 isothermal, irreversible free expansion

question 9.47 asks for ∆S, ∆Ssurr and ∆Stotal for an isothermal irreversible free expansion of an ideal gas. why is it that the solutions manual assumes ∆U=0 for this system?

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### Re: 9.47 isothermal, irreversible free expansion

The question refers to an isothermal process. When temperature is constant, ∆U=0.

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### Re: 9.47 isothermal, irreversible free expansion  [ENDORSED]

Isothermal processes do not involve a change in temperature. This means $\Delta T$ is 0. Dr. Lavelle went over the relationship that states $\Delta U$ = $3/2 nR\Delta T$
Any isothermal process thus implies that the internal energy change, $\Delta U$ is 0.