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List the characteristics of Gibbs free energy. |
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Answer» Solution :(i) Free energy is defined as G = H - TS 'G' Is a state function. (ii) G - Extensive property ,`DeltaG` intensive property. When mass REMAINS CONSTANT between initial and final state of system. (iii) 'G' has a single value for the THERMODYNAMIC state of the system. (iv) `G and DeltaG` value correspond to the system only. `{:("Process","Spontaneous","Equilibrium","Non-spontaneous"),(DeltaG,-Ve,"zero",+Ve):}` Gibbs free energy and the net work DONE by the system: For any system at constant pressure and temperature `DeltaG=DeltaH-TDeltaS""...(1)` We known that, `DeltaH=DeltaU+PDELTAV` `:.DeltaG = DeltaU+PDeltaV-TDeltaS` from first law of thermodynamics `DeltaU=q+w` form second law of thermodynamics `DeltaS=(q)/(T)DeltaG=q+w+PDeltaV-T((q)/(T))` `DeltaG=w+PDeltaV` `-DeltaG=-w-PDeltaV""...(2)` But `-PDeltaV` represent the work done due to expansion against a constant external pressure. |
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