Ionization Constants of Weak Acids Acid Formula Ka at 25 °C Lewis Structure acetic CH3CO2H 1.8 × 10−5 NaN arsenic H3AsO4 5.5 × 10−3 NaN arsenic NaN 1.7 × 10−7 NaN arsenic NaN 5.1 × 10−12 NaN arsenous H3AsO3 5.1 × 10−10 NaN boric H3BO3 5.4 × 10−10 NaN carbonic H2CO3 4.3 × 10−7 NaN carbonic NaN 4.7 × 10−11 NaN cyanic HCNO 2 × 10−4 NaN formic HCO2H 1.8 × 10−4 NaN hydrazoic HN3 2.5 × 10−5 NaN hydrocyanic HCN 4.9 × 10−10 NaN hydrofluoric HF 3.5 × 10−4 NaN hydrogen peroxide H2O2 2.4 × 10−12 NaN hydrogen selenide H2Se 1.29 × 10−4 NaN hydrogen selenide HSe– 1 × 10−12 NaN hydrogen sulfate ion NaN 1.2 × 10−2 NaN hydrogen sulfide H2S 8.9 × 10−8 NaN hydrogen sulfide HS– 1.0 × 10−19 NaN hydrogen telluride H2Te 2.3 × 10−3 NaN hydrogen telluride HTe– 1.6 × 10−11 NaN hypobromous HBrO 2.8 × 10−9 NaN hypochlorous HClO 2.9 × 10−8 NaN nitrous HNO2 4.6 × 10−4 NaN oxalic H2C2O4 6.0 × 10−2 NaN oxalic NaN 6.1 × 10−5 NaN phosphoric H3PO4 7.5 × 10−3 NaN phosphoric NaN 6.2 × 10−8 NaN phosphoric NaN 4.2 × 10−13 NaN phosphorous H3PO3 5 × 10−2 NaN phosphorous NaN 2.0 × 10−7 NaN sulfurous H2SO3 1.6 × 10−2 NaN sulfurous NaN 6.4 × 10−8 NaN