When a Reaction is defined, a Species node () is automatically generated for the participating reactants and products. This feature enables you to review and enter species specific information regarding chemical kinetics, thermodynamics and transport properties.

It is also possible to add and define an individual Species node: on the Chemistry toolbar click Species or right-click the Chemistry node and select it from the context menu.

When a Species node is automatically generated using the Formula text field for the Reaction node, the Species name is also automatically generated.

For a Species node added individually, enter a Species name in the field and click Apply.

Select a species type — Bulk species, Surface species, or Solvent.

Bulk species and Solvent are solved for volumetric concentrations (SI unit: mol/m3), while Surface species are solved for surface concentration (SI unit: mol/m2). The compositions for Bulk species and Solvent use the syntax c_speciesname, while Surface species uses csurf_speciesname_surf.

When Surface species is selected, the corresponding reaction formula introduces (ads) after the species notation and changes the species’ name to speciesname_surf. Additionally, the Species node name is updated in a similar fashion.

The General Parameters section deals with species parameters.

The default value for the Molar mass, M, and the ionic Charge, z, of the species is automatically defined from the species name by assuming that it corresponds to its chemical formula. Provided that the formula contains elements from the periodic table, the species molar mass is computed from mass the of occurring individual elements¹. When the species name contains parts not in the periodic table, for example when a descriptive name such as water is used, the molar mass is set to 0.0 kg/mol and the charge to zero. In this case, the molar mass needs to be defined in order to achieve mass balanced reactions and correct definitions of mass basis properties. The species charge is also deduced from the species name. Creating a H+ species, the charge will be set to one. When needed, both the Molar mass and the Charge can be edited in the corresponding edit field.

It is possible to specify the species density ρ when the fluid Mixture is specified as Liquid. The default value is that of water at 293 K.

Change the Automatic default setting to User defined to use a species reaction rate other than the one set up in the associated Reaction node. For individual species, use the User defined option to set a reaction rate other than zero (that is, nonreactive).

Edit either the Rate expression (SI unit: mol/(m3·s)), the Surface rate expression (SI unit: mol/(m2·s)), or both. For a bulk species, both expressions appear if surface reactions are present in the reactor since the reaction of the species can depend both on bulk reaction R and surface reaction Rads rates. For a surface species, only the surface reaction rate Rads appears.

The Additional Source section is available in order to include additional rate contribution for the species to the reaction kinetics. When the Additional source check box is selected, add an Additional rate expression in the text field (SI unit: mol/m3).

To account for non-ideality in the fluid mixture, adjust the activity coefficient in the Activity coefficient input field. This input field is only shown if activity instead of concentration has been chosen in the interface, that is, the Use activities check box is selected on the Chemistry interface Settings window

Click to select the Constant concentration/activity check box if the species concentration or activity should be treated as constant.

Choose the User defined alternative to specify Cp, h, and s directly.