例2用EDTA滴定Zn2至化学计量点附近, pH=11.00,NH3=0.10moL,计算 Igaz 解: ain(NH3)1+INH31P1+INH3182+INH31B3+INH31B4 =1+10-10227+10-2.01.61+103001.01+10-4.00+9.0 ≠1+10127+19201+10401+10506=10510 查表,pH=100时, gain(OH)=54 Zn Zn(NH Zn(OH)-1 1051+10 054-x=1056zn=5.6
22 例2 用EDTA滴定Zn2+至化学计量点附近, pH = 11.00，[NH3 ]= 0.10mol·L-1 , 计算 lgZn Zn(NH3)=1+[NH3 ] 1+[NH3 ] 2 2+[NH3 ] 3 3+[NH3 ] 4 4 =1+10-1.00+2.27+10-2.00+4.61+10-3.00+7.01+10-4.00+9.06 =1+101.27+102.61+104.01+105.06 = 105.10 查表, pH=11.00时, lgZn(OH)= 5.4 Zn ＝ Zn(NH3 )+ Zn(OH) - 1 ＝ 105.1 + 105.4 - 1 = 10 5.6 lgZn = 5.6 解:
例3用EDTA滴定Zn2至化学计量点附近, pH=9.0,c(NH)=0.10moL,计算 Igain(NH3 解:CNH)=NHJH+NH+∑Zm(NH3 NH,I 忽略 K(N)=103(7=0.1) CNHD 3 aNH3 (H) l+[H]·k(NH4) 1+109.0+9.4=10.5 23
23 例3 用EDTA滴定Zn2+至化学计量点附近, pH=9.0，c(NH3 )=0.10mol·L-1 ,计算lgZn(NH3 ). ( ) ( ) 3 + H + NH H 4 3 3 - + -9.37* a 4 9.0+9.4 0.5 (NH ) = = 1+[H ] (NH ) [NH ] = 1+1 (NH ) = 10 = 1 0 = 10 K I 0. c K 3 [Zn(NH ) ] i 3 [NH ] 忽略 c(NH3 )=[NH3 ]+[NH4 + 解: ]+
c(NH3)10 INHa- dNH3(H)100 10-15=0.03molL 5 10-94×0.1 或:[NH2]=x0·C(NH2)= 1090+10394 =0.03mol.L1 Ln(NH3) 1+[NH31B+[NH31B2+ B3+NH314B4 =1032 lgazn(NH3 =3.2 24
24 ( ) -1 3 -1.5 -1 3 0.5 NH H 3 (NH ) 10 [NH ] = = = 10 = 0.03 mol L 10 c ( ) = 3.2 Zn NH3 lg Zn(NH3 ) = 1+[NH3 ] 1+[NH3 ] 2 2+[NH3 ] 3 3+[NH3 ] 4 4 3.2 = 10 x c( ) 或 -9.4 3 0 3 -9.0 -9.4 : 10 0.1 [NH ] = NH = 10 +10 -1 = 0.03 mol L
3.络合物的副反应系数-aMY M Y H OH MHY M(ORY 计算:pH=30、5.0时的a/mYm (查表,K(ZnHY)=1030) pH=3.0,aznY(m=1+103030=2 pH=5.0,anY(m=1+105030=1 25
25 计算：pH=3.0、5.0时的αZnY(H) (查表, K(ZnHY)=103.0) pH=3.0, αZnY(H)=1+10-3.0+3.0=2 pH=5.0, αZnY(H)=1+10-5.0+3.0=1 3. 络合物的副反应系数 - αMY H+ OH－ MHY M(OH)Y M + Y = MY
42.3络合物的条件(稳定)常数 K' (MY)=I(MY)'I [MYlaMr K(MY MY IMTY MITYJayay Bp: lgK(MY)=Ig K(MY)+lgaMy-lgaM-lga 通常lgK(MY)=lgK(MY)-lgay-gaM 仅Y有副反应:gK(MY)=K(MY)-gay 仅M有副反应:lgK(MY=gK(MY)-gaM 26
26 4.2.3 络合物的条件(稳定)常数 ( ) MY M Y MY M Y [(MY) ] [MY] MY = = = (MY) [M ][Y ] [M][Y] K K Y lg (MY K ) = lg (MK Y )- lg M lg (MK Y) = lg (MK Y) -lg 仅Y有副反应: 仅M有副反应: MY M Y 即：lg (MY) = lg (MY)+lg -lg -lg K K Y M 通常 lg (MY) = lg (MY) - lg - lg K K