*H *as function of *P* and *T*. Integration of gives:

(101)

For an ideal gas:

(102)

As shown in (103) the integral in (101) is zero and *H* for an ideal gas is not a function of *P*

(103)

Expanding the lower integration boundary we get:

(104)

Combination of the first two terms of the right hand side of (104) yields *H* for a *hypothetical ideal gas*. In addition, for an ideal gas mixture there is no excess *H*

(105)