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Sourav posted an Question

August 20, 2020 • 18:36 pm

30 points

IIT JAM
Chemistry (CY)

Gibbs free energy the function that is particularly applicable to constant pressure is called gibbs free energy and it is denoted by 'g it is given by - g h-ts

Plz explain how dG = Wmax - Wexp , is it bcoz - A = Wrev = w max?

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Priyanshu kumar Best Answer

Sourav,this is gibbs free energy and in previous query there it is helmholtz free energy... The Gibbs' free energy is the energy available to do non-PV work in a thermodynamically-closed system at constant pressure and temperature. The Helmholtz free energy is the maximum amount of "useful" (non-PV) work that can be extracted from a thermodynamically-closed system at constant volume and temperature
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in helmholtz free energy you derive the relation by keeping volume constant....but here as gas expands and work of expansion is also there...volume is not constant
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Sourav

sir what work is actually wrev and how is it different from wexp
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Sourav here volume changes and work done by the gas on expansion against the external pressure
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sir i want to know how Wmax is different from Wexp?
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The reversible expansion does the maximum amount of work because the gas is pushing against the maximum possible external pressure.
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here reversible expansion works is produced
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As the gas expands here,it does work on the surrounding
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then what is Wexp? it is also work of expansion na?
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yes here work of expansion and as maximum work is obtained due to reversible process
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can we say wmax is wrev and wexp is wirr?
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here by doing this we get maxm useful work by considering these both work...Wmax and Wexp
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Here we get net work sourav by subtracting the maximum work due to reversible process and work of expansion by the gas against the external pressure
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then if we are getting max useful work by - dA =wrev why we are using - dG=Wmax - Wexp?
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sir if it is asked what is the max useful work without giving any condition, we will write dA or dG?
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Priyanshu kumar

Yes sourav,as in your previous query you see -delA=Wrev=Wmax
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Reversible process produce the maximum amount of work...So Wrev=Wmax
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You think it correctly 👍
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