I am a new user and I have a simple question to ask

[zyh_0604]

When I start to use the soft,I find a problem that I can not deal with. Firstly I did a small experiment using the soft,I want to see the result

of the action between Ag+ and Cl-.In the SpecE8 module,I populated the Basis only with Ag+ and Cl-, and set both their amount at a concentration of 1 mg\kg,and the mass of H2o is 1 free kg,last I set the temperature at 25℃, this is the situation of the basis.I used the pane of "Run",then I saw a surprising result:

Aqueous species molality mg/kg sol'n act. coef. log act.

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

Cl- 2.771e-005 0.9825 0.9950 -4.5595

Ag+ 8.778e-006 0.9468 0.9950 -5.0588

AgCl 4.917e-007 0.07047 1.0000 -6.3083

AgCl2- 1.187e-009 0.0002122 0.9950 -8.9278

AgCl3-- 3.322e-014 7.116e-009 0.9803 -13.4873

AgCl4--- 1.709e-018 4.267e-013 0.9562 -17.7868

I do not understand that the amount of AgCl is so small,and why the amount of Cl- was so large,the situation of Ag+ is as well.Please help me explain it thank you！

[Brian Farrell]

Hi,

 

I don't know too much about the Ag-Cl system specifically, but perhaps you are expecting a higher degree of complexation in your fluid? In general, the ionic strength is a good indicator of whether fluid components like Ag+ and Cl- will be present as free ions or associated as ion pairs/ complexes. Your fluid is very dilute, so it would make sense that the Ag+ and Cl- would be present almost entirely as free ions. In a system with more Cl-, a larger percentage of the Ag+ will be present as complexes. Perhaps you should compare the log K for the reaction AgCl = Ag+ + Cl- in the databases distributed with GWB and in the literature.

 

Another thing to keep in mind, for future reference, is that SpecE8 does not enforce charge balance by default. Adding two components (with different molecular weights) of 1 mg/kg each produces a fluid that cannot exist. For rough calculations this may be fine, of course, but it is something to consider.

 

Hope this helps,

 

Brian Farrell

Aqueous Solutions LLC