The Finite Rate Chemistry model, as implemented in CFX, assumes that the rate of progress of elementary reaction k can be reversible only if a backward reaction is defined. Therefore, the rate of progress R k, is computed as:
 | (7–11) |
where [ I ] is the molar concentration of component I and F k and B k are the forward and backward rate constants respectively.
r represent the reaction order of component I in the elementary reaction k. This reaction order is equal to the stoichiometric coefficient for elementary reactions, but it can be different for certain global reactions.
The only built-in formula for the forward and backward rate constants assumes an Arrhenius temperature dependence as:
 | (7–12) |
 | (7–13) |
where:
A k is pre-exponential factor
is
the temperature exponent (dimensionless)E k is the activation energy
T is the absolute temperature
can also be specified
directly without using relations.
Separate sets of coefficients 
, 
and 
are applied to forward
and backward rates.