Acid Ionization Constants at 25 °C.

Acid Formula Ka

Acetic acid HC2H3O2 1.8×10–5

Acrylic acid HC3H3O2 5.5×10–5

Aluminum 3+ ion Al3+(aq) 1.4×10–5

Ammonium ion NH4+ 5.6×10–10

Anilinium ion C6H5NH3+ 1.4×10–5

Arsenic acid H3AsO4 6.0×10–3

  H2AsO4– 1.0×10–7

  HAsO42– 3.2×10–12

Arsenous acid H3AsO3 6.6×10–10

Ascorbic acid H2C6H6O6 6.8×10–5

  HC6H6O6– 2.8×10–12

Bromoacetic acid HC2H2BrO2 1.3×10–3

Benzoic acid HC7H5O2 6.3×10–5

Beryllium 2+ ion Be2+(aq 3×10–7

Boric acid H3BO3 5.9×10–10

Butyric acid HC4H7O2 1.5×10–5

Carbonic acid H2CO3 4.4×10–7

  HCO3– 4.7×10–11

Chloroacetic acid HC2H2ClO2 1.4×10–3

Chlorous acid HClO2 1.1×10–2

Chromic acid H2CrO4 1.5×10–1

  HCrO4– 3.2×10–7

Chromium 3+ ion Cr3+(aq) 6.6×10–4

Citric acid H3C6H5O7 7.4×10–4

  H2C6H5O7– 1.7×10–5

  HC6H5O72– 4.0×10–7

Cobalt 2+ ion Co2+(aq) 1.3×10–9

Codeine ammonium ion HC18H21O3N+ 1.1×10–8

Cyanic acid HOCN 3.5×10–4

Dichloroacetic acid HC2HCl2O2 5.5×10–2

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

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 peroxide H2O2 2.2×10–12

Hydrogen selenate ion HSeO4– 2.2×10–2

Hydrogen sulfate ion HSO4– 1.1×10–2

Hydroselenic acid H2Se 1.3×10–4

  HSe– 1×10–11

Hydrosulfuric acid H2S 1.0×10–7

  HS– 1×10–19

Hydrotelluric acid H2Te 2.3×10–3

  HTe– 1.6×10–11

Hydroxylammonium ion HONH3+ 1.1×10–6

Hypobromous acid HOBr 2.5×10–9

Hypochlorous acid HClO 2.9×10–8

Hypoiodous acid HOI 2.3×10–11

Hyponitrous acid H2N2O2 (HON=NOH) 8.9×10–8

  HN2O2– (HON=NO–) 4×10–12

Iodic acid HIO3 1.6×10–1

Iodoacetic acid HC2H2IO2 6.7×10–4

Iron 2+ ion Fe2+(aq) 3.2×10–10

Iron 3+ ion Fe3+(aq) 6.3×10–3

Isoquinolinium ion HC9H7N+ 4.0×10–6

Lactic acid HC3H5O3 1.3×10–4

Malonic acid H2C3H2O4 1.5×10–3

  HC3H2O4– 2.0×10–6

Methylammonium ion CH3NH3+ 2.4×10–11

Morphinium ion HC17H19O3N+ 1.4×10–8

Nickel 2+ ion Ni2+(aq) 2.5×10–11

Nitrous acid HNO2 7.2×10–4

Oxalic acid H2C2O4 5.4×10–2

  HC2O4– 5.3×10–5

Phenol C6H5OH 1.0×10–10

Phenylacetic acid HC8H7O2 4.9×10–5

Phosphoric acid H3PO4 7.1×10–3

  H2PO4– 6.3×10–8

  HPO42– 4.2×10–13

Phosphorous acid H3PO3 3.7×10–2

  H2PO3– 2.1×10–7

Piperidinium ion HC5H11N+ 7.7×10–12

Propionic acid HC3H5O2 1.3×10–5

Pyridinium ion C5H5NH+ 6.7×10–6

Pyrophosphoric acid H4P2O7 3.0×10–2

  H3P2O7– 4.4×10–3

  H2P2O72– 2.5×10–7

  HP2O73– 5.6×10–10

Pyruvic acid HC3H3O3 1.4×10–4

Quinolinium ion HC9H7N+ 1.6×10–5

Selenous acid H2SeO3 2.3×10–3

  HSeO3– 5.4×10–9

Succinic acid H2C4H4O4 6.2×10–5

  HC4H4O4– 2.3×10–6

Sulfurous acid H2SO3 1.3×10–2

  HSO3– 6.2×10–8

Thiophenol HSC6H5 3.2×10–7

Trichloroacetic acid HC2Cl3O2 3.0×10–1

Triethanolammonium ion HC6H15O3N+ 1.7×10–8

Triethylammonium ion (C2H5)3NH+ 1.9×10–11

Trimethylammonium ion (CH3)3NH+ 1.5×10–10

Urea hydrogen ion NH2CONH3+ 6.7×10–1

Zinc 2+ ion Zn2+(aq) 2.5×10–10