Equilibrium Constant Forms

van ‘t Hoff Equation (van_t_hoff)

The method uses the van ‘t Hoff equation to calculate the equilibrium constant.

\[k_{eq} = k_{eq, ref} e^{-(\frac{\Delta H_{rxn}}{R})(\frac{1}{T} - \frac{1}{T_{ref, eq}})}\]

Parameters

Symbol	Parameter Name	Units	Description
\(k_{eq, ref}\)	k_eq_ref	Varies, depends on equilibrium form	Equlibrium constant at reference temperature
\(T_{ref, eq}\)	temperature_eq_ref	Base units	Reference temperature for calculating equilibrium constant

Gibbs Energy (gibbs_energy)

The method uses the thermodynamic relationship with Gibbs energy to calculate the equilibrium constant. This form is only supported for reactions using a molarity or activity basis due to challenges associated with automatically converting concentrations to other bases.

Note that by convention (for aqueous systems at least), the standard units of k_eq in this form are \((mol/L)^{order}\), which will be converted to the correct units automatically.

\[k_{eq} = e^{-\frac{\Delta H_{rxn, ref}}{R T} + \frac{\Delta S_{rxn, ref}}{R}}\]

Parameters

Symbol	Parameter Name	Units	Description
\(\Delta H_{rxn, ref}\)	dh_rxn_ref	Base units	Heat of reaction at reference temperature
\(\Delta S_{rxn, ref}\)	ds_rxn_ref	Base units	Entropy of reaction at reference temperature
\(T_{ref, eq}\)	temperature_eq_ref	Base units	Reference temperature, used for calculating scaling factors