Chemical Equilibrium Calculation


This spreadsheet will calculate the chemical equilibrium state of an ideal gas mixture, subject to necessary constraints on two intrinsic variables. Depending on the constraint chosen, the calculation invokes STANJAN to minimize the appropriate derived property—Gibbs energy, Helmholz energy, internal energy, enthalpy—or maximize entropy for the user-supplied gas mixture.

At this time all species must be gaseous; the calculator will not consider multiple phases. Thus, while solid and liquid species are present in the database they cannot be included in the equilibrium calculation.

Starting Temperature:

Starting Pressure:


Estimated Equilibrium Temperature:


Estimated Equilibrium Pressure:



Calculation Constraints

Exactly one constraint must be selected for each calculation. Please select one of the following:

Constant pressure and temperature


Constant volume and temperature

Constant temperature and entropy


Constant pressure and volume

Constant pressure and enthalpy


Constant pressure and entropy

Constant volume and internal energy


Constant volume and enthalpy

Constant volume and entropy





Please provide a list of elements present in the gas mixture. Elements present in the database may be found here


Reactant Mixture Composition


Species Name

Moles or
Mole Fraction


Additional Species

Please list any additional species that may be present at equilibrium. It it not necessary to re-enter the reactant species listed above. Only those species listed below and as reactants will be considered in the calculation.


    Having trouble? Please click on the button
to see a list of recognized species names