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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: san1984 on April 19, 2006, 08:47:45 AM

Title: Question on Gibbs free energy
Post by: san1984 on April 19, 2006, 08:47:45 AM

This question was posed by my lecturer on Gibbs free energy, please share your thoughts.

The question goes like this :

delta G = delta U - TdeltaS - PdeltaV
           = W_rev + PdeltaV

-delta G = -W_rev - PdeltaV

-W_rev - PdeltaV is reversible work, exclusive of reversible work, also referred as net work.

so -delta G = -W'_rev  (net work)

We know that gibbs free energy is a state function. But why is that for different pathways from the same initial state to the same final state in free energy, the net work for each pathway can be different when the equation -delta G = -W'_rev holds true ?

ie. delta G = NetWork1, delta G = NetWork2, delta G = NetWork3

but NetWork1 is not equal to NetWork2 or NetWork3 but delta G is the same.


 

Title: Re: Question on Gibbs free energy
Post by: susak on May 01, 2006, 12:36:41 PM

Derivation you showed works only in isobaric-isothermic conditions (constant temperature and pressure). By these conditions, when the process is reversible, the non-expansion work is equal to the change of Gibbs energy.