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Reference Tables and Other Information for Chemistry
Dissociation Constants: Ka and Kb Values
Dissociation constants (Ka and Kb) for weak acids and weak bases provide a measure of the extent to which the acid or base dissociates in water. This page provides a list of common weak acids and bases and their Ka and Kb values. Learn more about dissociation constants in our Acids and Bases Chapter of the Chemistry Tutorial.
The dissociation constant data in the tables below have been found in a variety of sources. They is not firm agreement on all values, particularly in the second significant digit. All reported values are applicable at temperatures of 25°C. We have ordered the acids and bases alphabetically by name and organized them into tables by type - e.g., weak acids, polyprotic acids, strong acids, etc.
Ka Values of Weak Acids
| Name |
Formula |
Ka |
| Acetic acid |
HC2H3O2 |
1.8×10-5 |
| Acrylic acid |
HC3H3O2 |
5.5×10-5 |
| Benzoic acid |
HC7H5O2 |
6.3×10-5 |
| Bromoacetic acid |
HC2H2BrO2 |
1.3×10-3 |
| Butanoic acid |
HC4H7O2 |
1.5×10-5 |
| Chloroacetic acid |
HC2H2ClO2 |
1.4×10-3 |
| Chlorous acid |
HClO2 |
1.1×10-2 |
| Cyanic acid |
HOCN |
3.5×10-4 |
| Dichloroacetic acid |
HC2HCl2O2 |
5.5×10-2 |
| Dihydrogen borate ion |
H2BO3- |
1.8x10-13 |
| Dihydrogen phosphate ion |
H2PO4- |
6.3x10-8 |
| Fluoroacetic acid |
HC2H2FO2 |
2.6×10-3 |
| Formic acid |
HCHO2 |
1.8×10-4 |
| Hydrazinium ion |
N2H5+ |
1.2×10-8 |
| Hydrazoic acid |
HN3 |
1.9×10-5 |
| Hydrocyanic acid |
HCN |
6.2×10-10 |
| Hydrofluoric acid |
HF |
6.6×10-4 |
| Hydrogen borate ion |
HBO32- |
1.6x10-14 |
| Hydrogen carbonate ion |
HCO3- |
4.7x10-11 |
| Hydrogen oxalate ion |
HC2O4- |
5.4 x 10-5 |
| Hydrogen peroxide |
H2O2 |
2.2×10-12 |
| Hydrogen phosphate ion |
HPO42- |
4.2x10-13 |
| Hydrogen selenate ion |
HSeO4- |
2.2×10-2 |
| Hydrogen sulfate ion |
HSO4- |
1.1×10-2 |
| Hydrogen sulfide ion |
HS- |
1.3x10-13 |
| Hydrogen sulfite ion |
HSO3- |
6.2x10-8 |
| Hydronium ion |
H3O+ |
1.00 |
| Hypobromous acid |
HOBr |
2.5×10-9 |
| Hypochlorous acid |
HClO |
2.9×10-8 |
| Hypoiodous acid |
HOI |
2.3×10-11 |
| Iodic acid |
HIO3 |
1.6×10-1 |
| Iodoacetic acid |
HC2H2IO2 |
6.7×10-4 |
| Lactic acid |
HC3H5O3 |
1.3×10-4 |
| Methanoic acid |
HCO2H |
1.8x10-4 |
| Nitrous acid |
HNO2 |
7.2x10-4 |
| Nitrous acid |
HNO2 |
7.2×10-4 |
| Phenol |
HOC6H5 |
1.6x10-10 |
| Phenylacetic acid |
HC8H7O2 |
4.9×10-5 |
| Propionic acid |
HC3H5O2 |
1.3×10-5 |
| Pyrophosphoric acid |
H4P2O7 |
3.0×10-2 |
| Pyruvic acid |
HC3H3O3 |
1.4×10-4 |
| Thiophenol |
HSC6H5 |
3.2×10-7 |
| Trichloroacetic acid |
HC2Cl3O2 |
1.3 x 10-4 |
| Uric acid |
HC5H3N4O3 |
6.7×10-1 |
| Water |
H2O |
1.0x10-14 |
Ka Values of Polyprotic Acids
| Name |
Formula |
Ka1 |
Ka2 |
Ka3 |
| Arsenic acid |
H3AsO4 |
6.0×10-3 |
1.0×10-7 |
3.2×10-12 |
| Arsenous acid |
H3AsO3 |
6.6×10-10 |
7.9×10-13 |
3.9×10-14 |
| Ascorbic acid |
H2C6H6O6 |
7.9x10-5 |
1.6×10-12 |
-- |
| Boric acid |
H3BO3 |
5.8x10-10 |
1.8x10-13 |
1.6 x 10-14 |
| Carbonic acid |
H2CO3 |
4.4×10-7 |
4.7×10-11 |
-- |
| Chromic acid |
H2CrO4 |
1.5×10-1 |
3.2×10-7 |
-- |
| Citric acid |
H3C6H5O7 |
7.4×10-4 |
1.7×10-5 |
4.1×10-7 |
| Hydroselenic acid |
H2Se |
1.3×10-4 |
1×10-11 |
-- |
| Hydrosulfuric acid |
H2S |
1.1 x 10-7 |
1.3 x 10-13 |
-- |
| Hydrotelluric acid |
H2Te |
2.3×10-3 |
1.6×10-11 |
-- |
| Hyponitrous acid |
H2N2O2 |
8.9×10-8 |
4×10-12 |
-- |
| Malonic acid |
H2C3H2O4 |
1.5×10-3 |
2.0×10-6 |
-- |
| Oxalic acid |
H2C2O4 |
5.4×10-2 |
6.5×10-5 |
-- |
| Phosphoric acid |
H3PO4 |
7.1×10-3 |
6.3x10-8 |
4.2x10-13 |
| Phosphorous acid |
H3PO3 |
5.0×10-2 |
2.0×10⁻⁷ |
-- |
| Selenous acid |
H2SeO3 |
2.3×10-3 |
5.4×10-9 |
-- |
| Succinic acid |
H2C4H4O4 |
6.2×10-5 |
2.3×10-6 |
-- |
| Sulfurous acid |
H2SO3 |
1.3×10-2 |
6.2×10-8 |
-- |
Ka Values of Strong Acids
| Name |
Formula |
Ka |
| Chloric Acid |
HClO3 |
1×103 |
| Hydrobromic acid |
HBr |
1.0x109 |
| Hydrochloric acid |
HCl |
1.3x106 |
| Hydroiodic acid |
HI |
2×109 |
| Nitric acid |
HNO3 |
2.4x101 |
| Perchloric acid |
HClO4 |
Large |
| Sulfuric acid |
H2SO4 |
1.0x103 |
Ka Values of Metal Ions
| Name |
Formula |
Ka |
| Aluminum 3+ ion |
Al3+ |
1.4×10-5 |
| Beryllium 2+ ion |
Be2+ |
3×10-7 |
| Chromium 3+ ion |
Cr3+ |
6.6×10-4 |
| Cobalt 2+ ion |
Co2+ |
1.3×10-9 |
| Iron 2+ ion |
Fe2+ |
3.2×10-10 |
| Iron 3+ ion |
Fe3+ |
6.3×10-3 |
| Nickel 2+ ion |
Ni2+ |
2.5×10-11 |
| Zinc 2+ ion |
Zn2+ |
2.5×10-10 |
Kb Values of Weak Bases
| Name |
Formula |
Kb |
| Ammonia |
NH3 |
1.8x10-5 |
| Aniline |
C6H5NH2 |
7.1x10-10 |
| Codeine |
C18H21O3N |
9.1x10-7 |
| Diethylamine |
(C2H5)2NH |
7.1x10-4 |
| Ethylamine |
C2H5NH2 |
4.3x10-4 |
| Ethylenediamine |
NH2CH2CH2NH2 |
5.3x10-4 |
| Hydroxylamine |
HONH2 |
9.1x10-9 |
| Isoquinoline |
C9H7N |
2.5x10-9 |
| Methylamine |
CH3NH2 |
4.2x10-4 |
| Morphine |
C17H19O3N |
7.1x10-7 |
| Piperidine |
C5H11N |
1.3×10-3 |
| Pyridine |
C5H5N |
1.5x10-9 |
| Quinoline |
C9H7N |
6.3x10-10 |
| Triethanolamine |
C6H15O3N |
3.3x10-14 |
| Triethylamine |
(C2H5)3N |
5.9x10-7 |
| Trimethylamine |
(CH3)3N |
5.3x10-4 |
| Urea |
NH2CONH2 |
6.7x10-5 |
Ka Values of Conjugate Acids of Weak Bases
| Name |
Formula |
Ka |
| Ammonium ion |
NH4+ |
5.6×10-10 |
| Anilinium ion |
C6H5NH3 |
1.4×10-5 |
| Codeine ammonium ion |
HC18H21O3N+ |
1.1×10-8 |
| Diethylammonium ion |
(C2H5)2NH2+ |
1.4×10-11 |
| Dimethylammonium ion |
(CH3)2NH2+ |
1.7×10-11 |
| Ethylammonium ion |
C2H5NH3+ |
2.3×10-11 |
| Ethylenediammonium ion |
NH2CH2CH2NH3+ |
1.9×10-11 |
| Hydroxylammonium ion |
HONH3+ |
1.1×10-6 |
| Isoquinolinium ion |
HC9H7N+ |
4.0×10-6 |
| Methylammonium ion |
CH3NH3+ |
2.4×10-11 |
| Morphinium ion |
HC17H19O3N+ |
1.4×10-8 |
| Pyridinium ion |
C5H5NH+ |
6.7×10-6 |
| Quinolinium ion |
HC9H7N+ |
1.6×10-5 |
| Triethanolammonium ion |
HC6H15O3N+ |
3.0×10-1 |
| Triethylammonium ion |
(C2H5)3NH+ |
1.7×10-8 |
| Trimethylammonium ion |
(CH3)3NH+ |
1.9×10-11 |
| Urea hydrogen ion |
NH2CONH3+ |
1.5×10-10 |
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