Acids and Bases: pKa and pKb

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Click here for theory about pH
Browse direct to the Table of pKa values for acids or Table of pKb values for bases. (Legend at the bottom of this page).
A list of commonly used HPLC-buffers with their working range and UV cutoff as well as other links to buffer-sites can be found elsewhere on the Laboratory-pages.

pH theory

The relationship between pH, pKa, and the relative concentrations of an acid and its salt is as follows:

[A^-] the molar concentration of the salt (dissociated species)
[HA] the concentration of the undissociated acid
When the concentrations of the salt and acid are equal, the pH of the system equals the pKa of the acid.

The percentage ionisation from a given pKa value can be calculated at Reall.

pKa and pKb tables

Make your choice: Table of pKa values for acids or Table of pKb values for bases. Click here for the abbreviations used in the tables. You can always return to this index by mouse-double click.


Acids	T(°C)	pKa	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14
Acetic acid	25	4.75
ACES	20	6.90
ADA	20	6.60
Benzoic acid	25	4.20
Bicine	20	8.35
BIS-TRIS Propane	20	6.80
o-Boric acid (1)	20	9.14
o-Boric acid (2)	20	12.74
o-Boric acid (3)	20	13.80
Carbonic acid (1)	25	6.37
Carbonic acid (2)	25	10.25
CAPS	20	10.40
CHES	20	9.50
Citrate (1)	25	3.13
Citrate (2)	25	4.76
Citrate (3)	25	6.40
Acids	T(°C)	pKa	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14
Diethylmalonic acid	-	7.20
Formic acid	20	3.75
Glycylglycine	20	8.40
HEPES	20	7.55
HEPPS	20	8.00
Imidazole	20	7.00
MES	20	6.15
MOPS	20	7.20
PIPES	20	6.80
Phenol	20	9.99
o-Phosphoric acid (1)	25	2.12
o-Phosphoric acid (2)	25	7.21
o-Phosphoric acid (3)	25	12.67
POPSO	-	7.85
Succinic acid (1)	-	4.19
Succinic acid (2)	-	5.57
TAPS	25	8.40
TES	20	7.50
Tricine	20	8.15
TRIS	20	8.30

Bases	T(°C)	pKb	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Ammonia	25	9.25
Aniline	25	4.63
Benzylamine	25	9.33
n-Butylamine	20	10.78
Diethylamine	20	11.09
Dimethylamine	25	10.73
Diphenylamine	25	0.79
Ethylenediamine	20	10.81
Ethylenediamine (1)	20	10.08
Ethylenediamine (2)	20	6.99
Methylamine	25	10.66
N-Methylaniline	25	4.85
Morpholine	25	8.33
Pyridine	25	5.21
Triethylamine	18	11.01
Trimethylamine	25	9.81

Abbreviations

ACES 2-[(2-amino-2-oxoethyl)amino]ethanesulphonic acid
ADA N-(2-acetamido)-2-iminodiacetic acid
BES N,N-bis( 2-hydroxyethyl)-2-aminoethanesulphonic acid
BICINE n,n-bis(2-hydroxyethyl) glycine
BIS-TRIS-Propane 1 ,3-bis[tris(hydroxymethyl)methylamino] propane
CAPS 3-(cyclohexylamino) propanesulphonic acid
CHES 2- (cyclohexylamino) ethanesulphonic acid
HEPES N-2-hydroxyethylpiperazine-N'-2-ethane-sulphonic acid
HEPPS N-2-hydroxycthylpipcrazine-N'-3-propane-sulphonic acid
MES 2-(N-morpholino) ethanesulphonic acid
MOPS 3-(N-morpholino) propanesulphonic acid
PIPES piperazine-N-N’-bis (2-ethanesulphonic acid)
POPSO piperazine-1,4-bis(2-hydroxypropanesulfonic acid)
TAPS 3-[tris (hydroxymethyl) methyl] amino propanesulphonic acid
TES 2-[tris (hydroxymothyl) methyl] amino ethanesulphonic acid
Tricine N-[tris (hydroxymethyl) methy] glycine
TRIS tris (hydroxylmethyl) aminomethane

last update: augustus 11, 2007