In general, chemical reactions can be described in terms of K elementary reactions involving N _C components that can be written as:

(7–2)

where is the stoichiometric coefficient for component in the elementary reaction . The stoichiometric coefficients for reactants are denoted by a single dash, , and those for products by a double dash, .

The rate of production/consumption, , for component can be computed as the sum of the rate of progress for all the elementary reactions in which component participates:

(7–3)

where is the elementary reaction rate of progress for reaction , which in CFX can be calculated using the Eddy Dissipation Model or/and the Finite Rate Chemistry Model. is the molar mass of component .