Thermodynamics of Formation any Useful?

[toupis12]

Hello everyone, I was able to find a paper (attached) with thermodynamic data for minerals of my interest. I would like to add them to the database, but the thermodynamics are only for the formation of these minerals and not their dissolution that the database seems to be using. Do I get meaningful data by using log K and enthalpy of formation? Or does anybody have an idea how I can use the data in the paper to add these minerals to the databases?

Thank you for any potential replies,

[dlparkhurst]

It looks like the paper gives free energy of formation of the minerals. You can use that information to estimate a log K for a dissolution reaction, but, you must write a reaction and then estimate free energies of formation for all of the aqueous species in the reaction. The sum of the free energies (products minus reactants) give delta G of reaction, and

delta G of reaction = -2.303RTlog10(K)

Tables of free energies of species vary, which produces uncertainty and possibly inconsistency in the log10 K that you determine. Note that log10 K of the dissolution reaction is simply the negative of the formation reaction. For the temperature dependence relationships with enthalpy and other quantities, you must look at a basic thermodynamics text.

[toupis12]

Thank you so much! Exactly what I needed to bring it home.