For a reversible process involving only pressure-volume work
A
[ <p><span>A. (dF)<sub>T, P</sub> <p><span>B. (dF)<sub>T, P</sub> > 0
B
(dF)<sub>T, P</sub> = 0
C
(dA)<sub>T, V</sub>
Correct Answer: (dF)<sub>T, P</sub> = 0
Here the $$F$$ is Gibbs free energy and $$A$$ is Helmholtz free energy.Since for an reversible process $$Tds = dU + PdV$$
For, constant temperature and constant pressure process the above equation can be written as
$$\eqalign{ & d\left( {TS - U} \right) = PdV \cr & \Rightarrow d\left( { - A} \right) > PdV \cr & \Rightarrow {\left( {dF} \right)_{T,\,P}} = 0. \cr} $$
For reversible process.
