Derive Gibbs Energy change and non mechanical work.
Gibbs free energy is that thermodyanamic quantity of a system is whose value during a process is equal to the maximum possible useful work that can be obtained from the system.
, q=∆U+wexpansion + wnon-expansion …1
Under constant pressure condition
, q=∆U +P∆V +wnon-expansion =∆H + wnon-expansion ……2
For reversible change taking place at constant tempreture
∆S=qrev/T or qrev=T∆S ……3
From 2 & 3
T∆S=∆H + wnon-expansion or ∆H-T∆S=-wnon-expansion
Under constant tempreture and pressure,
∆G=∆H-T∆S
At the end,
∆G=-wnon-expansion = non mechanical work (maximum)