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Acid Ionization Constants at 25 oC.





Substance 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 H2C6H6 O6 6.8×10–5
  HC6H6O6 2.8×10–12
Bromoacetic acid HC2H2BrO 2 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 H3C6H5 O7 7.4×10–4
  H2C6H5 O7 1.7×10–5
  HC6H5O7 2– 4.0×10–7
Cobalt 2+ ion Co2+(aq) 1.3×10–9
Codeine ammonium ion HC18H21O 3N+ 1.1×10–8
Cyanic acid HOCN 3.5×10–4
Dichloroacetic acid HC2HCl2O2 5.5×10–2
Diethylammonium ion (C2H5)2 NH2+ 1.4×10–11
Dimethylammonium ion (CH3)2NH 2+ 1.7×10–11
Ethylammonium ion C2H5NH3 + 2.3×10–11
Ethylenediammonium ion NH2CH2CH2 NH3+ 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 H2C3H2 O4 1.5×10–3
  HC3H2O4 2.0×10–6
Methylammonium ion CH3NH3+ 2.4×10–11
Morphinium ion HC17H19O 3N+ 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
  H2P2O7 2– 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 H2C4H4 O4 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 HC6H15O3 N+ 1.7×10–8
Triethylammonium ion (C2H5)3 NH+ 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