Hi, Brian:
I have a follow-up question about calculating the equilibrium constant for the custom minerals. I did some calculations of lepidocrocite based on the Van't Hoff equation, the thermodynamic values I found for this mineral and other components for the dissolution reaction FeOOH+3H+--->Fe+++ +2H2O. The calculated Keq seems very small (logKeq=-0.00046 at 25 degree C), much lower than the value reported for dissolution constant (logKsp=log([Fe+++]/[H+]^3)) reported in literature (logKsp=1.39 reported in Schwertmann, Solubility and dissolution of iron oxides, Plant and Soil, 130, 1-25). For this reaction, my understanding about the Keq and Ksp is that they are the same. I am curious which values I should use. Because for another mineral I was planning to add, there is no solubility information but free energy, so I have to use the energy method to calculate equilibrium constant and am concerned about the accuracy.
Please advise and thanks a lot!
Yiran