TdS Equations

• For a closed system contaning a pure compressible substance undergoing a reversible process.

	(24.22)
or (per unit mass)	(24.23)

This is the famous Gibbsian equation.

• Eliminate du by using the definition of enthalpy

(24.24)

Thus,

(24.25)

(24.26)

Also,

(24.27)

• Important: These equations relate the entropy change of a system to the changes in other properties : . Therefore, they are independent of the process .

These relations can be used for reversible as well as irreversible processes.