In the Reaction Thermodynamics subnode (), the Enthalpy of Reaction (SI unit: J/mol) of each reaction can be specified. This node overrides all the automatically calculated reaction enthalpies as defined in the Species Thermodynamics subnode.

Add the Reaction Thermodynamics node from the Reaction Engineering toolbar, Attributes menu. Alternatively, when the Energy Balance is set to Include, right-click a Reversible Reaction Group or Equilibrium Reaction Group and select it from the context menu.