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Topic: Hello! First post on Physical Chemistry - ENTROPY CHANGE  (Read 8813 times)

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orthoformate

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Re: Hello! First post on Physical Chemistry - ENTROPY CHANGE
« Reply #15 on: July 07, 2016, 10:10:44 AM »
In this case, yes. More generally ΔSsurr = -Qsys/Tsurr
But I still disagree with your value of ΔV. How did you get it?

I made a calculation error. you are right. ΔV= 0.0156 m3

so W=1,013,250 Pa*0.0156 m3=15806.7 J

so ΔS= ∫PdV/T

so ΔS= 15806.7 J/T

how can we determine the temperature of the surroundings?

mjc123

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Re: Hello! First post on Physical Chemistry - ENTROPY CHANGE
« Reply #16 on: July 07, 2016, 11:22:12 AM »
I guess you're meant to assume it's the same as that of the gas, unless you are told otherwise. As the change is isothermal, and heat can flow between the gas and surroundings, we should assume they are in thermal equilibrium before and after the change (if not necessarily during).

orthoformate

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Re: Hello! First post on Physical Chemistry - ENTROPY CHANGE
« Reply #17 on: July 07, 2016, 12:50:29 PM »
I guess you're meant to assume it's the same as that of the gas, unless you are told otherwise. As the change is isothermal, and heat can flow between the gas and surroundings, we should assume they are in thermal equilibrium before and after the change (if not necessarily during).

Ah ok.

ΔSsurr=62.48 J/K
ΔSsys=-4.3 J/K

ΔSuniverse=58.18 J/K

Thank you for your help. This has been very enlightening.
« Last Edit: July 07, 2016, 03:00:21 PM by orthoformate »