If you are using the finite-rate model with reversible reactions (see Direct Use of Finite-Rate Kinetics (no TCI) in the Theory Guide), you must define the standard state entropy, for each species . These inputs are used to define the mixture entropy as

(8–73)

where is the molecular weight of the ^th species with units of kg/kmol and is the reference temperature at which is defined. Standard state entropies are input in units of J/kmol-K in SI units or in units of Btu/mol-°R in British units.

For each species involved in the reaction (that is, each fluid material contained in the mixture material), you can set the Standard State Entropy and Reference Temperature in the Create/Edit Materials Dialog Box.