18.2C Acidity of carboxylic acids Most unsubtituted carboxylic acids have Ka values in the range of 10-4-10-(pka=4-5) COoH CooNa t Naoh t ho Benzoic acid(pKa=4.15) Sodium benzoate (苯甲酸钠) (water insoluble) (water soluble co2H+ NaHCO3— -CO2Na CO2 H2018.2C Acidity of carboxylic acids Most unsubtituted carboxylic acids have Ka values in the range of 10-4—10-5 (pka = 4-5). COOH + NaOH COONa + H2O Benzoic acid Sodium benzoate (water insoluble) (water soluble) （ 苯 甲 酸 钠 ） CO2H + NaHCO3 CO2Na + CO2 + H2O (pKa = 4.15)