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Mineralogical reactions and thermodynamics (fwd)

Sender: Dean Biddle <dbiddle@waite.adelaide.edu.au>
Subject: WSN: Mineralogical reactions and thermodynamics


Could I please have feedback on the following approach for
calculating the spontaneity of mineralogical reactions from
elementary thermodynamics.  If anyone can tell me of references
existing for this approach, I would be greatful.

The following spreadsheet, with cell formulas listed at the
bottom, can be used to derive the magnitude of entropy, enthalpy
and Gibb's free energy of mineralogical reactions.


          A              B      C       D      E      F       G       H
1             Standard Thermodynamic Quantities of Reaction @ 25 =F8C
2
3                     react1  react2  react3        prod1   prod2   prod3
4       formula ---> NaAlSi3O   H+     H2O   --->  Al(OH)3  H4SiO4   Na+
5   coefficient --->     1       1      7             1        3      1
6       S (J/K-mol)    207.4       0   69.95         68.44     180     58.4
7       H (kJ/mol)   -3935.1       0 -285.83       -1293.1   -1460   -240.3
8       G (kJ/mol)   -3711.7       0 -237.14       -1154.9   -1308   -261.9
9
10   Order             -30.2
11   Endothermic        22.5
12   Nonspontaneous     30.92

where the active cell formulas are:

A10:  @IF(B10=3D0,"No Change",@IF(B10>0,"Disorder","Order"))
A11:  @IF(B11=3D0,"No Change",@IF(B11>0,"Endothermic","Exothermic"))
A12:  @IF(B12=3D0,"At Equilibrium",@IF(B12>0,"Nonspontaneous","Spontaneous"=
))
B10:  (F$5*F6)+(G$5*G6)+(H$5*H6)-(B$5*B6)-(C$5*C6)-(D$5*D6)
B11:  (F$5*F7)+(G$5*G7)+(H$5*H7)-(B$5*B7)-(C$5*C7)-(D$5*D7)
B12:  (F$5*F8)+(G$5*G8)+(H$5*H8)-(B$5*B8)-(C$5*C8)-(D$5*D8)


Mineral dissolution reaction can be written in many forms with
Al(OH)2+, Al(OH)3=F8, etc written as the products.  Changes in
product species leads to considerable changes in the spontaneity
of the reaction.

Please send replies to my email address:

               dbiddle@waite.adelaide.edu.au

Regards,

Dean Biddle.

                         From: Dean Biddle
                         University of Adelaide
                         Soil Science Dept
                         Waite Agricultural Res. Institute
                         Private Mail Bag No.1
                         Glen Osmond, South Australia, 5064.
                         Phone: (08) 303 7247
                         FAX: (08) 303 6511
                         Home Phone: (08) 379 0671
                         Email: dbiddle@waite.adelaide.edu.au



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