例4:计算pH为20和50时的K'(ZnY) Zn+Y→ZnY OH H aZn(OH) aRCH any (h) Ig K(zny)=16.5 lg k(znhy)=3.0
27 例4: 计算pH为2.0和5.0时的lgK (ZnY) lg (ZnY) K = 16.5 Zn + Y ZnY OH－ H＋ H＋ Zn(OH) Y(H) ZnY(H) H lg (ZnHY K ) = 3.0
pH=2.0 gay=13. 8, gain(oH) aLnY(h) 1+[H|K(ZnHY)=1+1020+3.0=1010 Ig K'(Zny)=Ig K(Zny)+Igazny(H-g Zn(OH)"& dr() =16.5+1.0-0.0-13.8=3.7 pH=50 Igay(6.6, gain(OH)=0.0 Ig K'(ZnY)=lg K(ZnY)-IgaY(=9.9 随pH升高,a(m减小,gK'(ZnY)增大
28 ZnY(H) Zn(OH) Y(H) lg (ZnY) = lg (ZnY) + lg - lg - lg = 16.5 +1.0- 0.0-13.8 = 3.7 K K Y(H) Y(H) Zn(OH) lg = 6.6, lg = 0.0 lg (ZnY) = lg ZnY - lg = pH = 5.0 K K 9.9 ( ) 随pH升高, Y(H) 减小, lgK (ZnY)增大. pH=2.0 lgY(H)=13.8, lgZn(OH)=0 ZnY(H)=1+[H+ ]KH(ZnHY)=1+10-2.0+3.0=101.0
lgK(ZnY)pH曲线 18 lgK(zny) 14 lgK(∠n 12 10 Igk(znY) 8 6 HgK'(ZpM) Zn(oh) 2 0 02468101214 29
29 lgK (ZnY)~pH曲线 0 2 4 6 8 10 12 14 16 18 0 2 4 6 8 10 12 14 pH lgK 16.5 lgK(ZnY) lgK(ZnY´ ) lgK ´(ZnY) lgK´(ZnY) lgaZn(OH) lgaY(H)
lgK(MY)~pH曲线 18 Ni2+ F Cd2+ IgK(FeY)=25.1 12 F Ig K(cuY)=18.8 2+ Ca IgK(Ay=16.1 Al Zn 2 024 101214 p 30
30 lgK (MY)~pH曲线 lgK(FeY) = 25.1 lgK(CuY) = 18.8 lgK(AlY) = 16.1 2 4 6 8 1 0 1 2 1 4 1 6 1 8 0 2 4 6 8 1 0 1 2 1 4 p H l gK (MY)' Fe3+ Hg2+ Al3+ Zn2+ Cu2+ Mg2+ Ca2+ Fe2+ Cd2+ Ni2+ lgK (MY) pH
例5计算pH=9.0,c(NH3)=01moL1 时的lgK(ZnY)。 Zn ZnY NH*<NH,Oh Zn(NH 3) Zn(OH) HY <n= Zn(NH3) Zn(oh) =10 3.2 +10 0.2 3.2 1=10 Ig K'(ZnY)=Ig K(ZnY)-Igazn-Igay( =16.5-3.2-1.4=11.9
31 例5 计算pH=9.0，c(NH3 ) = 0.1mol·L-1 时的 lg (ZnY) K . Zn Y(H) lg (ZnY) = lg (ZnY) - lg - lg = 16.5- 3.2-1.4 = 11.9 K K NH4 + ⎯ H+ Zn + Y ZnY NH3 OH- H+ Zn(NH3 ) Zn(OH) HY Zn Zn(NH ) Zn(OH) 3 3.2 0.2 3.2 - 1 = 10 +10 -1 = 10 = +