List the characteristics of Gibbs free energy.

Explanation

(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.