The activity of a substance, which is a function of temperature, pressure and composition, is defined as follows: 

where f̅^o_i (T,P^o, x^o) is the standard-state fugacity of species i at the standard-state pressure P^o and standard-state composition x^o (which could be the pure component state or one of the various Henry’s law standard states).

a. Using this definition of the activity, prove for a binary mixture at constant temperature and pressure that 

b. For fixed standard-state temperature, derive an expression for how the species activity changes with temperature at constant pressure and composition.

Transcribed Image Text:

a; (T, P, x) = fi (T, P, x) fi (T, P°, 2°)