Equilibrium constants of H2S(g)

[yuetingchen]

Recently, I looked at the equilibrium constants of H2S(g) in the GWB database (thermo.tdat). I believe some of the values are not right, and I’d like to share my observation with everyone. Below is what extracted from “thermo.tdat”:

 

-------------------------------------------------------------------------------------

H2S(g)

mole wt.= 34.0758 g

2 species in reaction

1.000 H+ 1.000 HS-

-8.0615 -7.9791 -7.9737 -8.0646

-7.1449 -4.6551 .4746 9.3231

------------------------------------------------------------------------------------------

The above data indicate that H2S(g) becomes more soluble when temperature increases above 100oC. That is at odds with my understand of gases solubilities in water, i.e., in general gases become less soluble with temperature increase.

 

I understand that “thermo.tdat” is based on EQ3/6 database data0, but I cannot tell which version of LLNL’s “data0” is used to generate “thermo.tdat”. I checked the YMP version of EQ3/6 database: “data0.ymp.R2”. Below is what I found for H2S(g) from this database:

 

------------------------------------------------------------------------

H2S(g)

sp.type = gas

* EQ3/6 = ymp.R2, ymp.R0, com, ree, alt, sup

YMP Qualification status = Q

* mol.wt. = 34.082 g/mol

V0PrTr = 0.000 cm**3/mol [source: 78hel/del]

****

2 element(s):

2.0000 H 1.0000 S

****

3 species in aqueous dissociation reaction:

-1.0000 H2S(g) 1.0000 H+

1.0000 HS-

*

**** logK grid [0-25-60-100C @1bar; 150-200-250-300C @Psat-H2O]:

-8.0781 -7.9759 -7.9295 -7.9572

-8.0759 -8.2750 -8.5671 -9.0074

*

* gflag = 1 [25C,1bar: reported delG0f used]

* P-T extrapolation algorithm: Cp(T), const-V(P) integration

* P-T extrapolation alg. ref.: 82wag/eva, N/A

* reference-state data source: 82wag/eva

* delG0f = -8.021 kcal/mol

* delH0f = -4.931 kcal/mol

* S0PrTr = 49.185 cal/(mol*K)

* Cp coefficients [source: 60kel ]

* T**0 = 0.78100000E+01

* T**1 = 0.29600000E-02

* T**-2 = -0.46000000E+05

* Tlimit = 2026.85C

-----------------------------------------------------------------------

The trend of temperature dependence of log K data appears making more sense.

 

[Brian Farrell]

For anyone who comes across this old post, the comments at the top of thermo.tdat indicate that it was based on the EQ3/6 dataset data0.3245r46. If you have other EQ3/6 datasets you prefer to work with in the GWB, please note that in GWB 2023 the TEdit app can be used to import any EQ3/6 dataset to GWB format. And conversely, GWB datasets using the b-dot and h-m-w models can be exported to EQ3/6 format. For more information, please see 9.3.2 Importing EQ3/6 datasets and 9.3.3 Exporting EQ3/6 datasets in the GWB Essentials Guide.

Regards,

Brian Farrell
Aqueous Solutions