Dissociation constants of some acids and bases at 25°C

click here for alphabetical order click here for pKa values
Acid (formula)       Ka1       Ka2       Ka3
Sulfuric acid (H2SO4) very big 1.20×10−02  
Oxalic acid (H2C2O4) 5.90×10−02 6.40×10−05  
Sulfurous acid (H2SO3) 1.70×10−02 6.40×10−08  
Phosphoric acid (H3PO4) 7.52×10−03 6.23×10−08 3.60×10−13
Ferric ion (Fe(H2O)63+) 4.00×10−03    
Nitrous acid (HNO2) 4.60×10−04    
Hydrofluoric acid (HF) 3.53×10−04    
Acetylsalicylic acid (aspirin HC9H7O4) 3.00×10−04    
Arsenic acid (H3AsO4) 2.50×10−04 5.60×10−08 3.00×10−13
Formic acid (HCOOH) 1.80×10−04    
Ascorbic acid (H2C6H6O6) 7.90×10−05 1.60×10−12  
Benzoic acid (HC6H5COO) 6.46×10−05    
Acetic acid (HCH3COO) 1.76×10−05    
Propionic acid (HC2H5COO) 1.34×10−05    
Aluminum ion (Al(H2O)43+) 1.20×10−05    
Carbonic acid (H2CO3) 4.30×10−07 5.61×10−11  
Hydrosulfuric acid (H2S) 1.00×10−07 1.00×10−19  
Hypochlorous acid (HclO) 3.50×10−08    
Hydrocyanic acid (HCN) 4.93×10−10    
Zinc ion (Zn(H2O)42+) 2.50×10−10    
Phenol (C6H5OH) 1.30×10−10    
Hydrogen peroxide (H2O2) 2.40×10−12    
Water (H2O) Kw = 1.00×10−14    

Base Formula Kb
PiperidineC5H11N1.32×10−03
Zinc hydroxideZn(OH)29.60×10−04
Diethylamine(C2H5)2NH6.90×10−04
Dimethylamine(CH3)2NH5.40×10−04
Triethylamine(C2H5)3N5.20×10−04
EthylamineC2H5NH24.30×10−04
CaffeineC8H10N4O24.10×10−04
MethylamineCH3NH23.70×10−04
Trimethylamine(CH3)3N6.45×10−05
Ammonium hydroxideNH4OH1.79×10−05
AmmoniaNH31.77×10−05
CodeineC18H21O3N1.63×10−06
MorphineC17H19O3N1.62×10−06
NicotineC10H14N21.05×10−06
HydroxylamineNH2OH9.10×10−09
IsoquinolineC9H7N2.50×10−09
PyridineC5H5N1.78×10−09
QuinolineC9H7N6.30×10−10
AnilineC6H5NH24.270×10−10
Water H2OKw = 1.00×10−14
Handbook of Chemistry and Physics. 64th Ed. R. C. Weast Editor. CRC Press, Inc. Boca Raton Florida. 1983-84. D-164 to D-169