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Variables in reversible isothermal vs isolated system
Posted: Wed Feb 14, 2018 2:58 pm
What exactly are all of the values that equal zero in an isolated system (or bomb calorimeter) vs in a reversible isothermal system?
I know that:
w = 0
deltaH = 0
deltaU = 0
w = 0?
what happens to q, and delta S, in these? /anything else important that I am forgetting?
Re: Variables in reversible isothermal vs isolated system
Posted: Wed Feb 14, 2018 3:17 pm
And delta S should equal zero for reversible.
Re: Variables in reversible isothermal vs isolated system [ENDORSED]
Posted: Wed Feb 14, 2018 3:22 pm
The qtot = qsys + qsurr = 0 for an isolated system.
For a reversible, isothermal system work is most definitely not 0. Recall the expression w = -nRTln(V2/V1) for an isothermal reversible process. Also, q is +nRTln(V2/V1) for isothermal reversible so that q + w = ΔU = 0.
You would calculate entropy changes for each system using ΔSsys = qrev/T. For the isolated system, this all depends on the value of qsys. In an isothermal reversible system it is ΔS = nRln(V2/V1).
Note that only ΔStot = 0 for reversible processes. ΔSsys can still take on a nonzero value.