The reaction rate for a bulk species of index k, being added to the bulk due to surface reactions is defined as
Rb,k (SI unit: mol/(s·m
2)).
with Mk (SI unit: kg/mol) being the molar mass of the species.
where ρk is the species density (SI unit: kg/m
3).
The bulk concentration, cb,k (SI unit: mol/m
2), for species
k is governed by the equation: