Equilibrium Reaction

Use this node to model an equilibrium reaction, involving two or more species, in a domain. Note that a necessary requirement for this is feature to be available is that two or more species are solved for by the interface.

The equilibrium reaction is defined by the relation between the chemical activities of the chemical species participating in the reaction (the equilibrium condition) and the stoichiometry of the reaction.

The node solves for an additional degree of freedom (the reaction rate) to fulfill the equilibrium condition at all times in all space coordinates.

If the check box is selected, the specified inflow concentration values in all active boundary nodes for the physics interface are modified to comply with the equilibrium condition.


	This feature is only available in a limited set of add-on products. See http://www.comsol.com/products/specifications/ for more details on availability.

Equilibrium Condition

The list defaults to or select . For either option, the check box is selected by default.

For , enter an Keq (dimensionless). The default is 1. Enter a value or expression for the Ca0 (SI unit: mol/m3). The default is 1·10-3 mol/m3. creates an equilibrium condition based on the stoichiometric coefficients, the species activities, and the law of mass action.

For , enter an Eeq (dimensionless).

Stoichiometric Coefficients

Enter a value for the stoichiometric coefficientνc (dimensionless). The default is 0. Use negative values for reactants and positive values for products in the modeled reaction.

Species with a stoichiometric coefficient value of 0 are not affected by the node.