6.12: Acid-Base Ionization Constant
- Page ID
- 371722
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John Moore, Jia Zhou, and Etienne Garand
Ionization Constants for Select Acids (a table for bases is below)
Ka determined at 25 °C.
Acid | Formula and Ionization Equation | Ka | pKa |
---|---|---|---|
Acetic | CH₃COOH + H₂O ⇌ H₃O⁺ + CH₃COO⁻ | 1.8 × 10⁻⁵ | 4.74 |
Arsenic | H₃AsO₄ + H₂O ⇌ H₃O⁺ + H₂AsO₄⁻ | K₁ = 6.17 × 10⁻³ | 2.210 |
H₂AsO₄⁻ + H₂O ⇌ H₃O⁺ + HAsO₄²⁻ | K₂ = 1.17 × 10⁻⁷ | 6.932 | |
HAsO₄²⁻ + H₂O ⇌ H₃O⁺ + AsO₄³⁻ | K₃ = 3.09 × 10⁻¹² | 11.523 | |
Benzoic | C₆H₅COOH + H₂O ⇌ H₃O⁺ + C₆H₅COO⁻ | 1.2 × 10⁻⁴ | 3.92 |
Boric | B(OH)₃(H₂O) + H₂O ⇌ H₃O⁺ + B(OH)₄⁻ | 5.8 × 10⁻¹⁰ | 9.24 |
Butyric | CH₃CH₂CH₂COOH + H₂O ⇌ H₃O⁺ + CH₃CH₂CH₂COO- | 1.5 × 10⁻⁵ | 4.82 |
Carbonic | H₂CO₃ + H₂O ⇌ H₃O⁺ + HCO₃⁻ | K₁ = 4.3 × 10⁻⁷ | 6.37 |
HCO₃⁻ + H₂O ⇌ H₃O⁺ + CO₃²⁻ | K₂ = 4.7 × 10⁻¹¹ | 10.33 | |
Citric | H₃C₆H₅O₇ + H₂O ⇌ H₃O⁺ + H₂C₆H₅O₇⁻ | K₁ = 1.4 × 10⁻³ | 2.85 |
H₂C₆H₅O₇⁻ + H₂O ⇌ H₃O⁺ + HC₆H₅O₇²⁻ | K₂ = 4.5 × 10⁻⁵ | 4.35 | |
HC₆H₅O₇²⁻ + H₂O ⇌ H₃O⁺ + C₆H₅O₇³⁻ | K₃ = 1.5 × 10⁻⁶ | 5.82 | |
Chloroacetic | CH₂ClCOOH + H₂O ⇌ H₃O⁺ + CH₂ClCOO- | 1.4 × 10-3 | 2.85 |
4-chlorobutyric | CH₂ClCH₂CH₂COOH + H₂O ⇌ H₃O⁺ + CH₂ClCH₂CH₂COO- | 3.0 × 10-5 | 4.53 |
3-chlorobutyric acid | CH₃CHClCH₂COOH + H₂O ⇌ H₃O⁺ + CH₃CHClCH₂COO- | 8.9 × 10-5 | 4.05 |
2-chlorobutyric acid | CH₃CH₂CHClCOOH + H₂O ⇌ H₃O⁺ + CH₃CH₂CHClCOO- | 1.3 × 10-3 | 2.89 |
Chlorous | HClO₂ + H₂O ⇌ H₃O⁺ + ClO₂⁻ | 1.1 × 10⁻² | 1.96 |
Dichloroacetic | CHCl2COOH + H₂O ⇌ H₃O⁺ + CHCl2COO- | 4.5 × 10-2 | 1.35 |
Formic | HCOOH + H₂O ⇌ H₃O⁺ + HCOO⁻ | 1.8 × 10⁻⁴ | 3.75 |
Hydrazoic | HN₃ + H₂O ⇌ H₃O⁺ + N₃⁻ | 1.0 × 10⁻⁵ | 5.00 |
Hydrochloric | HCl + H₂O ⇌ H₃O⁺ + Cl- | 1.2 × 106 | -6.1 |
Hydrocyanic | HCN + H₂O ⇌ H₃O⁺ + CN⁻ | 3.3 × 10⁻¹⁰ | 9.48 |
Hydrofluoric | HF + H₂O ⇌ H₃O⁺ + F⁻ | 6.8 × 10⁻⁴ | 3.17 |
Hydrogen peroxide | H₂O₂ + H₂O ⇌ H₃O⁺ + HO₂⁻ | 2.1 × 10⁻¹² | 11.68 |
Hydrosulfuric† | H₂S + H₂O ⇌ H₃O⁺ + HS⁻ | K₁ = 1 × 10⁻⁷ | 7.0 |
HS⁻ + H₂O ⇌ H₃O⁺ + S²⁻ | K₂ = 1 × 10⁻¹⁹ | 19.0 | |
Hypobromous | HOBr + H₂O ⇌ H₃O⁺ + OBr- | 3 × 10-9 | 8.5 |
Hypochlorous | HOCl + H₂O ⇌ H₃O⁺ + OCl⁻ | 6.8 × 10⁻⁸ | 7.17 |
Hypoiodous | HOI + H₂O ⇌ H₃O⁺ + OI- | 3 × 10-11 | 10.5 |
Nitric | HNO₃ + H₂O ⇌ H₃O⁺ + NO₃- | 27 | -1.43 |
Nitrous | HNO₂ + H₂O ⇌ H₃O⁺ + NO₂⁻ | 7.41 × 10⁻⁴ | 3.130 |
Oxalic | H₂C₂O₄ + H₂O ⇌ H₃O⁺ + HC₂O₄⁻ | K₁ = 5.5 × 10⁻² | 1.26 |
HC₂O₄⁻ + H₂O ⇌ H₃O⁺ + C₂O₄²⁻ | K₂ = 1.4 × 10⁻⁴ | 3.85 | |
Phenol | HC₆H₅O + H₂O ⇌ H₃O⁺ + C₆H₅O⁻ | 1.7 × 10⁻¹⁰ | 9.77 |
Phosphoric | H₃PO₄ + H₂O ⇌ H₃O⁺ + H₂PO₄⁻ | K₁ = 7.2 × 10⁻³ | 2.14 |
H₂PO₄⁻ + H₂O ⇌ H₃O⁺ + HPO₄²⁻ | K₂ = 6.3 × 10⁻⁸ | 7.20 | |
HPO₄²⁻ + H₂O ⇌ H₃O⁺ + PO₄³⁻ | K₃ = 4.6 × 10⁻¹³ | 12.34 | |
Phosphorous | H₃PO₃ + H₂O ⇌ H₃O⁺ + H₂PO₃⁻ | K₁ = 2.4 × 10⁻² | 1.62 |
H₂PO₃⁻ + H₂O ⇌ H₃O⁺ + HPO₃²⁻ | K₂ = 2.9 × 10⁻⁷ | 6.54 | |
Propanoic | CH₃CH₂COOH + H₂O ⇌ H₃O⁺ + CH₃CH₂COO⁻ | 1.33 × 10⁻⁵ | 4.85 |
Selenic | H₂SeO₄ + H₂O ⇌ H₃O⁺ + HSeO₄⁻ | K₁ = very large | --- |
HSeO₄⁻ + H₂O ⇌ H₃O⁺ + SeO₄²⁻ | K₂ = 2.2 × 10⁻² | 1.66 | |
Selenous | H₂SeO₃ + H₂O ⇌ H₃O⁺ + HSeO₃⁻ | K₁ = 2.5 × 10⁻³ | 2.60 |
HSeO₃⁻ + H₂O ⇌ H₃O⁺ + SeO₃²⁻ | K₂ = 1.6 × 10⁻⁹ | 8.80 | |
Sulfuric | H₂SO₄ + H₂O ⇌ H₃O⁺ + HSO₄⁻ | K₁ = 4.0 × 103 | -3.6 |
HSO₄⁻ + H₂O ⇌ H₃O⁺ + SO₄²⁻ | K₂ = 1.1 × 10⁻² | 1.96 | |
Sulfurous | H₂SO₃ + H₂O ⇌ H₃O⁺ + HSO₃⁻ | K₁ = 1.7 × 10⁻² | 1.77 |
HSO₃⁻ + H₂O ⇌ H₃O⁺ + SO₃²⁻ | K₂ = 6.3 × 10⁻⁸ | 7.2 | |
Tellurous | H₂TeO₃ + H₂O ⇌ H₃O⁺ + HTeO₃⁻ | K₁ = 7.1 × 10⁻⁷ | 6.15 |
HTeO₃⁻ + H₂O ⇌ H₃O⁺ + TeO₃²⁻ | K₂ = 4.0 × 10⁻⁹ | 8.40 | |
Trichloroacetic | CCl3COOH + H₂O ⇌ H₃O⁺ + CCl3COO- | 0.17 | 0.77 |
Trifluoroacetic | CF3COOH + H₂O ⇌ H₃O⁺ + CF3COO- | 0.30 | 0.52 |
Taken from Hogfeldt, E. and Perrin, D. D., Stability Constants of Metal-Ion complexes, 1st ed. Oxford: New York: Pergamon, 1979-1982. International Union of Pure and Applied Chemistry Commission on Equilibrium Data.
Also from Serjeant, E. P. and Dempsey, B. (eds.), “Ionization Constants of Organic Acids in Aqueous Solution,” IUPAC Chemical Data Series No. 23, Pergamon Press, Oxford, 1979.
†From Myers, R., Journal of Chemical Education, Vol. 63, 1986, pp. 687-690.
Ionization Constants for Select Bases
Kb determined at 25 °C.
Base | Formula and Ionization Equation | Kb | pKb |
---|---|---|---|
Acetylide | C₂H- + H₂O ⇌ OH- + C₂H₂ | 1 × 1011 | -11 |
Amide | NH₂- + H₂O ⇌ OH- + NH₃ | 1 × 1020 | -20 |
Ammonia‡ | NH₃ + H₂O ⇌ NH₄⁺ + OH- | 1.77 × 10⁻⁵ | 4.752 |
Aniline§ | C₆H₅NH₂ + H₂O ⇌ C₆H₅NH₃⁺ + OH- | 3.9 × 10⁻¹⁰ | 9.41 |
Dimethylamine§ | (CH₃)₂NH + H₂O ⇌ (CH₃)₂NH₂⁺ + OH- | 5.8 × 10⁻⁴ | 3.24 |
Ethoxide | CH₃CH₂O- + H₂O ⇌ OH- + CH₃CH₂OH | 1 × 102 | -2 |
Ethylenediamine | (CH₂)₂(NH₂)₂ + H₂O ⇌ (CH₂)₂(NH₂)₂H⁺ + OH- | K₁ = 7.8 × 10⁻⁵ | 4.11 |
(CH₂)₂(NH₂)₂H⁺ + H₂O ⇌ (CH₂)₂(NH₂)₂H₂²⁺ + OH- | K₂ = 2.1 × 10⁻⁸ | 7.68 | |
Hydrazine | N₂H₄ + H₂O ⇌ N₂H₅⁺ + OH- | K₁ = 1.2 × 10⁻⁶ | 5.92 |
N₂H₅⁺ + H₂O ⇌ N₂H₆²⁺ + OH- | K₂ = 1.3 × 10-15 | 14.89 | |
Hydride | H- + H₂O ⇌ OH- + H₂ | 1 × 1021 | -21 |
Hydroxylamine | NH₂OH + H₂O ⇌ NH₃OH⁺ + OH- | 9.3 × 10⁻⁹ | 8.03 |
Methylamine | CH₃NH₂ + H₂O ⇌ CH₃NH₃⁺ + OH- | 5.0 × 10⁻⁴ | 3.30 |
Pyridine | C₅H₅N + H₂O ⇌ C₅H₅NH⁺ + OH- | 1.6 × 10⁻⁹ | 8.80 |
Trimethylamine§ | (CH₃)₃N + H₂O ⇌ (CH₃)₃NH⁺ + OH- | 6.2 × 10⁻⁵ | 4.21 |
Taken from Hogfeldt, E. and Perrin, D. D., Stability Constants of Metal-Ion complexes, 1st ed. Oxford: New York: Pergamon, 1979-1982. International Union of Pure and Applied Chemistry Commission on Equilibrium Data.
Also from Serjeant, E. P. and Dempsey, B. (eds.), “Ionization Constants of Organic Acids in Aqueous Solution,” IUPAC Chemical Data Series No. 23, Pergamon Press, Oxford, 1979.
‡From Read, A. J., Journal of Solution Chemistry, Vol. 11, No. 9, 1982, pp. 649-664.
§From Meites, L., Ed. Handbook of Analytical Chemistry, 1st ed. New York: McGraw-Hill, 1963.