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BATE - pH Calculator
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BATE/Dissociation constants

Here are some of the values of weak and strong acids and bases dissociation constants used by BATE when calculating pH of the solution and concetrations of all ions present. So - if you dropped here looking just for constants check if the BATE will not make your calculations faster then you.

pKa and pKb values have been taken from various books and internet sources. Please remember that only some of them are included in the trial version database, but you can always enter them manually for calculations.

For the reactions of dissociation of acid:

dissociation reactions for two proton acid

stepwise dissociation constants are defined as

Ka1 and Ka2 definitions

Next dissociation steps are trated the same way. Dissociation can be also described by overall constants, as well as base dissociation constants or protonation constants. They are all defined in the help file accompanying BATE.

Acids
name formula pKan
acetic acid CH3COOH 4,75
citric acid C6H8O7 3,13
4,76
6,40
carbonic acid H2CO3 6,37
10,25
hydrochloric acid* HCl -4
hydrogen sulfide H2S 7,04
11,96
nitric acid* HNO3 -1
oxalic acid (COOH)2 1,25
4,27
perchloric acid* HClO4 -7
phenol C6H5OH 9,89
phosphoric acid H3PO4 2,15
7,20
12,35
sulphuric acid* H2SO4 -3
1,99

* see diclaimer at the bottom of this page.

For the reactions of dissociation of base:

dissociation reactions for base

stepwise dissociation constants are defined as

Kb1 and Kb2 definitions

Note that ammonia and most organic bases have to react with water before they can dissociate releasing OH- ion.

Bases
name formula pKbn
ammonia NH3 4,75
calcium hydroxide Ca(OH)2 2,43
1,4
lithium hydroxide LiOH 0,36
methylamine CH3NH2 3,36
ethylamine C2H5NH2N 3,25
potassium hydroxide KOH 0,5
sodium hydroxide NaOH 0,2
aniline C6H5NH2 9,4

Disclaimer - accuracy of the values shown, especially for the strong acids, is questionable. Depending on the source pKa for HCl is given as -3, -4 or even -7. These values are usually not measured but calculated from thermodynamical data and should not be treated too seriously. Besides, difference between pKa = -1 and pKa = -10 influences calculation results for the solutions with high ionic strength, which are dubious in any case. As for strong bases pKb values read explanation in our FAQ section.

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