《无机及分析化学》课程教学资源（PPT课件）第七章 酸碱平衡与酸碱滴定

酸碱平衡与酸碱滴定X一元弱碱在水中的电离B-+H,O一HB+OH[HB][OH]HBOHKb =Ko[A-]B例 NaAcHAc +OH-Ac- + H,O[(HAc)0]-[c(OH)[HAc] ·[OH]K6[Ac"]c(Ac

一元 弱碱在水中的电离 B- + H2O HB + OH-     c c B c c c HB Kb ( ) ] c(OH ) ] [ ( ) [ − −  = Kb = [HB][OH- ] [A- ] Ac− + H2O HAc +OH- 例 NaAc     c c Ac c c c HAc Kb ( ) ] c(OH ) ] [ ( ) [ − −  = [ ] [ ] [OH ] − −  = Ac HAc Kb

酸碱平衡与酸碱滴定X多元弱酸在水中的电离如：H,CO3CHCO.0] [C(H*H,CO3 +H,O =HCO3 + H,O6c(H,CO,)H,CO3 =HCO3 + H+HCO3 +H,O =CO2- + H,O+CCTa2HCO;=CO,2- + Hc(HCO

多元 弱酸在水中的电离 如：H2CO3 H2CO3 + H2O = HCO3 - + H3O+ H2CO3 = HCO3 - + H+ HCO3 - + H2O = CO3 2- + H3O+ HCO3 - = CO3 2- + H+     c c H CO c c c HCO Ka ( ) ] c(H ) ] [ ( ) [ 2 3 3 1 − +  =     c c HCO c c c CO Ka ( ) ] c(H ) ] [ ( ) [ 3 2 3 2 − − +  =

酸碱平衡与酸碱滴定X多元弱碱在水中的电离CO, 2-例：Na,CO3HCOKCO, 2- +H,O = HCO3- + OHCCOc(H,CO1.rc(OHHHCO3- +H,O =H,CO3 + OHc(HCO,根据酸碱共轭酸关系

多元 弱碱在水中的电离 例：Na2CO3 CO3 2- CO3 2- +H2O = HCO3 - + OH￾HCO3 - +H2O = H2CO3 + OH-     c c HCO c c c H CO Kb ( ) ] c(OH ) ] [ ( ) [ 3 2 3 2 − −  =     c c CO c c c HCO Kb ( ) ] c(OH ) ] [ ( ) [ 2 3 3 1 − − −  = 根据酸碱共轭酸关系

酸碱平衡与酸碱滴定X根据酸碱共轭酸关系一定有必然的联系K°与 H3. H+±B-HBCCHBCCHBOHB-+H,O HB + OHc(B两式相加为：c(Hc(OH-)TH,O = H+ + OHXWC000故° = pk = pk + pK?Kkg1Kod

根据酸碱共轭酸关系  Ka  与 Kb 一定有必然的联系 HB H＋＋B－ B- + H2O HB + OH-     c c B c c c HB Kb ( ) ] c(OH ) ] [ ( ) [ − −  =     c c HB c c c B Ka ( ) ] c(H ) ] [ ( ) [ +  = 两式相加为： H2O = H+ + OH-    c c OH c c H Kw ( ) ( ) + − =  故：  Ka  Kb =  Kw    pKw = pKa + pKb   a w b K K K =

酸碱平衡与酸碱滴定OX对多元酸：H,B对多元碱：B3-H,B =H,B- +H+B3- +H,O=HB2-+ OHe(HB")01-r(OH)[c(,Ra1rc(H0)oKahC(B3-c(H,B)H,B- = HB2- +H+HB2- +H,O =H,B-+ OHrC(HB2-rc(H,B-T01-TC(OHO110ToKoa2b2C(HB2c(H,BHB2- =B3- +H+H,B-+HO = H,B+ OH[C(B3)01.[c(H0][c(H,B)01-rc(OH )2KasC(HB2Kg?ec(H,B-)Ka-K = Kw关系:Ka2 - K2 = KwKa-K= Kw

对多元酸： H3 B B3-    Ka1 Kb3 = KW 关系：    Ka2 Kb2 = KW    Ka3 Kb1 = KW H3B = H2B- + H+ H2B- = HB2- + H+ HB2- = B3- + H+ B3- +H2O = HB2- + OH￾HB2- +H2O = H2B-+ OH￾H2B- +H2O = H3B+ OH-     c c H B c c c H B Ka ( ) ] c(H ) ] [ ( ) [ 3 2 1 +  =     c c H B c c c HB Ka ( ) ] c(H ) ] [ ( ) [ 2 2 2 − − +  =     c c HB c c c B Ka ( ) ] c(H ) ] [ ( ) [ 2 3 3 − − +  =     c c B c c c HB Kb ( ) ] c(OH ) ] [ ( ) [ 3 2 1 − − −  =     c c HB c c c H B Kb ( ) ] c(OH ) ] [ ( ) [ 2 2 2 − − −  =     c c H B c c c H B Kb ( ) ] c(OH ) ] [ ( ) [ 2 3 3 − −  = 对多元碱：