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pH calculator program - Base Acid Titration and Equilibria - dissociation constants pKa and pKb

BATE - pH calculator

BATE pH calculator

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pH calculator » dissociation constants



As someone who has to write intricate Excel worksheets for preparing buffers at our company, this program [Buffer Maker] seems amazing.

Tim Fitzwater

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.

For the definitions of Kan constants scroll down the page.

Acids
nameformulapKan
acetic (ethanoic) acidCH3COOH4.75
citric acidC6H8O73.13
4.76
6.40
carbonic acidH2CO36.37
10.25
hydrochloric acid*HCl-4
hydrogen sulfideH2S7.04
11.96
nitric acid*HNO3-1
oxalic acid(COOH)21.25
4.27
perchloric acid*HClO4-7
phenolC6H5OH9.89
phosphoric acidH3PO42.15
7.20
12.35
sulphuric acid*H2SO4-3
1.99

* see diclaimer below pKb table.

For the definitions of Kbn constants scroll down the page.

Note that ammonia and most organic bases release OH- ions due to hydrolysis, not dissociation. On the contrary inorganic bases - like NaOH, KOH, LiOH, Ca(OH)2 - increase pH dissociating.

Bases
nameformulapKbn
ammoniaNH34.75
calcium hydroxideCa(OH)22.43
1.4
lithium hydroxideLiOH-0.36
methylamineCH3NH23.36
ethylamineC2H5NH2N3.25
potassium hydroxideKOH0.5
sodium hydroxideNaOH0.2
anilineC6H5NH29.4

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 - NaOH, KOH, LiOH, Ca(OH)2 - pKb values read explanation in our FAQ section.

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

For the reactions of dissociation of base:

dissociation reactions for base

stepwise dissociation constants are defined as

Kb1 and Kb2 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.

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