### 8.11.2. Reactants/Products

Reactants and products are specified in terms of parent and child materials. The parent material defines the phase in which species react, and the child materials represent the reacting species. For this release of ANSYS CFX, reactants from different phases can only be specified for the char oxidation reactions (`Field Char Oxidation` or `Gibb Char Oxidation`). Arrhenius type multiphase reaction rates require that all reactants belong to the same phase. The stoichiometry for multiphase reactions is specified by means of mass coefficients rather than stoichiometry coefficients referring to moles.

#### 8.11.2.1. Example

As an example, consider a simplified case of coal reacting with oxygen in the reaction . The Parent Materials List on the Reactants tab contains two materials, `Coal` (a pure substance containing carbon) and `Gas mixture` (a variable composition mixture containing `O2`, `CO2` and `N2`). The child material for `Coal` would be set to `Carbon`, and the child material for `Gas Mixture` would be set to `O2`. It follows that on the Products tab, the Materials List contains `Gas Mixture` as the parent material, which in turn would contain `CO2` as its child.

Note: The above is presented only as an illustration of the use of the parent/child material structure.

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