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Information loss of H2 in minteq


csk
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Hello Everyone!

Recently I met some problem in drawing the Eh-pH diagrams of the element Mo using GWB12.0 and thermo.minteq because it doesn't include the information about the H2. And it can't produce the water limit line in the final Eh-pH diagram. And I also tried to use the information about H2 from the default database like thermo.tdat. But I found the detailed information of H2 was edited in different styles and sometimes I am also confused about some abbreviation. Therefore, I wonder if there any basic information about H2 edited in the format of thermo.minteq. Thanks

Xinyu

 

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Hi Xinyu,

Act2 needs reactions for O2(g) and H2(g) to draw the water stability limits. The thermo_minteq.tdat dataset does not contain a reaction for H2(g), however, so you’ll have to add it. Because the reaction for H2(g) is typically written in terms of H2(aq), there are actually two reactions you need to add:

H2(aq) + .5 O2(aq) = H2O (in the redox couples section)

H2(g) = H2(aq) (in the gases section)

These are the reactions you’ll find in the GWB’s default dataset, thermo.tdat. Each of these reactions has equilibrium constants (expressed as log Ks) at multiple principal temperatures. The principal temperatures differ between the two datasets, so you’ll need to make sure to specify the log Ks for the correct temperatures. In older versions of the GWB, you had to edit the datasets by hand in a text editor like Notepad, so this was easy to overlook. Now you can simply copy and paste (or drag and drop) an entry from one dataset to another using the TEdit app. Best of all, TEdit will automatically find matching principal temperatures and insert the log Ks in the correct locations.

For more on using TEdit to copy reactions, please see 9.2.6 Transferring dataset entries in the GWB Essentials Guide. For an older discussion of a similar topic, please see this thread.

Hope this helps,

Brian Farrell
Aqueous Solutions LLC
 

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