Aspen Physical Property System - Physical Property Models

electrolyte systems with infinite dilution aqueous reference state cannot be
used for electrolyte systems with the symmetric reference state for ionic
components.
The chemical constants for electrolyte systems with the symmetric reference
state can be written in these forms:
166 2 Thermodynamic Property Models
(87)
(88)
where i indicates a molecular or ionic component and h represents a Henry
component. Eq. 83 or 84 is used for calculation of the unsymmetric activity
coefficients of Henry components. However, the calculation for the activity
coefficients of ionic components is carried out with the symmetric reference
state.
Other Thermophysical Properties
The activity coefficient model can be related to other properties through fundamental
thermodynamic equations. These properties (called excess liquid functions) are relative to the
ideal liquid mixture at the same condition:
Excess molar liquid Gibbs free energy
Excess molar liquid enthalpy
Excess molar liquid entropy
(89)
(90)
(91)
The excess liquid functions given by Equations 89-91 are calculated from the
same activity coefficient model. In practice, however, the activity coefficient �i
is often derived first from the excess liquid Gibbs free energy of a mixture
from an activity coefficient model:
with
(92)
(93)
(94)