弱酸性药形 品砥性药彩 HAKaH+A Ka BH+. H+B (非解离型) (解离型)（非解离型) [H+][A] Ka= [H[B] Ka(解离常数)= [HA] [BH+] 双侧取负对数： 双侧取负对数： [A] -ogKa=-og[H门--log [B] -logKa=-log[H*]-log [HA] 因为-logKa=pKa;-log[Ht]=pH 因为-logKa=pKa;-log[Ht]=pH [B] 所以pKa=pH-log [A] [HA] 所WpKa=PH-Ho7 pH-pKa=log [A] =pH+log [BH] B) [HA] 10PH-pKa_ [A] KaH 即 [解离型] [HA] [非解离型] 10PKa-PH=[BH*] 即 [解离型] [非解离型]11