Table of Dissociation Constants for Acids and Bases (data adapted from CRC Handbook of Chemistry and Physics, 84th edition) Weak acids Weak acids typically donates a hydrogen ion to solution as demonstrated by the reaction: HA H++ A−HA H++ A− Ka is the equilibrium acid dissociation constant defined as: Ka=[H+][A−][HA]Ka=[H+][A−][HA] The pKa is then defined as −log(Ka). Polyprotic acids list the successive ionization steps under the “step” column. Inorganic acids (listed alphabetically) Formula step pKa Organic acids (listed by carbon number) Formula step pKaarsenic acid H3AsO41 2.26 formic acid CH2O21 3.75 2 6.76 acetic acid C2H4O21 4.76 3 11.29 acetic acid, fluoro- C2H3FO21 2.59 boric acid H3BO31 9.27 acetic acid, chloro- C2H3ClO21 2.87 carbonic acid H2CO31 6.35 acetic acid, bromo- C2H3BrO21 2.90 2 10.33 acetic acid, iodo- C2H3IO21 3.18 chloric acid group acetic acid, trifluoro- C2HF3O21 0.52 hypochlorous acid HClO 1 7.40 acetic acid, trichloro- C2HCl3O21 0.66 chlorous acid HClO21 1.94 acetic acid, nitro- C2H3NO41 1.48 chloric acid HClO31 strong acetic acid, cyano- C3H3NO21 2.47 perchloric acid HClO41 strong oxalic acid C2H2O41 1.25 chromic acid H2CrO41 0.74 2 3.81 2 6.49 acrylic acid C3H4O21 4.25 hydrocyanic acid HCN 1 9.21 pyruvic acid C3H4O31 2.39 hydrobromic acid HBr 1 strong propanoic acid C3H6O21 4.87 hydrochloric acid HCl 1 strong lactic acid C3H6O31 3.86 hydrofluoric acid HF 1 3.20 succinic acid C4H6O41 4.21 hydroiodic acid HI 1 strong 2 5.64 hydrogen sulfide H2S 1 7.05 butanoic acid C4H8O21 4.83 2 11.0 pentanoic acid C5H10O21 4.83 nitric acid HNO31 strong phenol C6H6O 1 9.99 nitrous acid HNO21 3.25 citric acid C6H8O71 3.13 phosphoric acid H3PO41 2.16 2 4.76 2 7.21 3 6.40 3 12.32 benzoic acid C7H6O21 4.20 pyrophosphate H4P2O71 0.91 1-methylphenol C7H8O 1 10.29 (also called diphosphate) 2 2.10 phthalic acid C8H6O41 2.94 3 6.70 2 5.43 4 9.32 acetylsalicylic acid (aspirin) C9H8O41 3.48 sulfuric acid H2SO41 strong 2 1.99 sulfurous acid H2SO31 1.85 2 7.20 telluric acid H2TeO41 7.68 2 11.0 water H2O 1 13.995Weak Bases Weak bases typically accept a hydrogen ion from water as demonstrated by the reaction: B + H2O(l) HB++ OH− Kb is the equilibrium base dissociation constant defined as: Kb=[HB+][OH−][B]Kb=[HB+][OH−][B] Note that H2O(l) does not appear in the equilibrium equation since it is a pure substance. The pKb is then defined as −log(Kb). Chemical (in order of carbon number) Formula step pKbammonia NH31 4.75 hydrazine N2H41 5.9 methylamine CH5N 1 3.34 ethylamine C2H7N 1 3.35 dimethylamine C2H7N 1 3.27 imidazole C3H4N21 7.01 propylamine C3H9N 1 3.46 trimethylamine C3H9N 1 4.2 pyridine C5H5N 1 8.77 pyridine, 4-chloro- C5H4ClN 1 10.17 pyridine, 4-nitro- C5H4N2O21 12.39 pyridine, 4-amino- C5H4N2H21 4.89 pyridine, 4-methyl- C6H7N 1 8.01 aniline C6H7N 1 9.13 aniline, 4-fluoro- C6H6FN 1 9.35 aniline, 4-chloro- C6H6ClN 1 10.02 aniline, 4-bromo- C6H6BrN 1 10.11 aniline, 4-iodo- C6H6IN 1 10.19 aniline, 4-nitro- C6H6N2O21 12.98 aniline, 4-methyl- C7H9N 1 8.92 triethylamine C6H15N 1