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Difference between reaction rate expression and equilibrium constant
Posted Jul 8, 2022, 11:27 a.m. EDT Chemical, Chemical Reaction Engineering 1 Reply
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Hello everyone.
I am working on the Transport of Diluted Species in Porous Media (tds) module and i have introduced an equilibrium reaction node. In the window of equilibrium reaction, I am defining the Keq (equilibrium constant) and stoichiometric coefficients only. These reactions are contributing the 'Ri' part in the mass balance equation, which is reaction rate expression with units (mol/m^3 *s).
My question is how COMSOL calculates the reaction rates (Ri) although the reactions are equilibrium reactions.
Also, I have 4 chemical reaction (equilibrium) with 6 species how is the system of equations is complete?
Thank you in advance.
the mass balance equation is. █(∂/(∂t ) (ϕc_i )+∇⋅J_i+q⋅∇c_i = R_i
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I have always failed to use equilibrium reactions in my models. Instead, I define an arbitrary high forward reaction rate constant (kf) and use the equilibrium constant K to define the backward rate constant (kb).
K = kf/kb --> kb = kf/K
This converges, not equilibria.
Lasse