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Definition of acid dissociation in water
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Topic: Definition of acid dissociation in water (Read 823 times)
Yongqiang
Top Contributor
Posts: 89
Definition of acid dissociation in water
«
on:
January 13, 2020, 08:07:38 AM »
Hi PHREEQC experts,
I want to model an organic acid (PTBBA) dissociation in the solution. I used the following method to do it. But no matter how much acid in the brine, the pH keeps at 7.0. Please share me some insights on this problem. Thank you very much.
Best Regards,
Yongqiang
DATABASE c:\phreeqc\database\LLNL.DAT
TITLE pH calculation
SOLUTION_MASTER_SPECIES
A A- -1.0 177.231 177.231
SOLUTION_SPECIES
A- = A-
log_k 0
A- + H+ = AH
log_k -4.4
SOLUTION 1
units mol/l
A 0.07
Na 0.355
Ca 0.045
Mg 0.045
Cl 0.534
END
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MichaelZ20
Top Contributor
Posts: 123
Re: Definition of acid dissociation in water
«
Reply #1 on:
January 13, 2020, 01:55:00 PM »
Add pH 7 charge to your SOLUTION 1
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Yongqiang
Top Contributor
Posts: 89
Re: Definition of acid dissociation in water
«
Reply #2 on:
January 13, 2020, 02:05:10 PM »
Hi Michael,
Thank you for your reply.
Yes, adding the pH 7 charge works.
I want to know that the pH usually adjusts itself when we do solution species calculation. Can you share any insights on whether to use the pH charge function during the definition of solution conditions?
Regards,
Yongqiang
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MichaelZ20
Top Contributor
Posts: 123
Re: Definition of acid dissociation in water
«
Reply #3 on:
January 13, 2020, 02:58:45 PM »
See:
http://phreeqcusers.org/index.php/topic,70.msg167.html#msg167
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Definition of acid dissociation in water