2个副反应同时存在时 M+ MoH]+M(oh),+---MA+MA, l+ [M] 啊]+[MOH+MOH2]+…+[M+MA+MA2]+…-[M [M M(OH)T a M(A) 若有n个副反应 aM-aM(al M(A2) M(An)(n
6 2个副反应同时存在时 2 M 2 [M]+[MOH]+M(OH) ]+---[MA]+[MA ]+-- = ] - [M 2 2 [M]+[MOH]+M(OH) ]+ +[M + [MA]+[MA ]+ = [M] ] -[M] = M(OH) M(A) + 1- M = M(A1)+ M(A2) +----- M(An)-(n-1) 若有n个副反应
例2用EDTA滴定Zn2至化学计量点附近, ph=11.00, NH31=0. 10mol L- 计算 lg a Ln(NH3) 1+INH31B+[ B2+INH313B3+INH314B =1+10-100+227+102.00+4.61+103.00+1.01+104.009.6 J+1032+102+10401+10506=10510 查附录6,pH=11.00时,10zmOm=5.4 1ga2n=g(am(NH+amoH1)=g(1051+10541)=1056
7 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 lg Zn 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 查附录III.6 , pH=11.00时, lg Zn(OH)=5.4 lg Zn= lg( Zn(NH3)+ Zn(OH)-1)=lg(105.1+105.4 -1)=10 5.6
例3用EDIA滴定Zm2至化学计量点附近, pH=9.0, C(NH3=0.10mol. L:, 计算lga Zn(NH3) c(NH=|NH+|NH+∑区zn(NH3)J INH2I 3 忽略 K2(NH)=1037(=0.1) INHa] 3 MNH3()[NH31 1+[H]K"(NH4 =1+10-90+94=1005
8 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lg Zn(NH3) c(NH3 )=[NH3 ]+[NH4 +]+ ( ) ( ) ( ) ] 3 + H + NH 4 + -9.37* a 4 3 -9.0+9.4 0. 3 H 5 [NH = = 1+[H ] NH [NH ] = 1+1 (NH ) 1 = 0. = 0 = 0 1 K 0 I 1 K 3 [Zn(NH ) ]i 3 [NH ] 忽略
NH 0.1 NH E 3 =0.03=10-1mo|.L 05 NH3(H) 100 或 109;4×0.1 NH,|= 3」--0 =0.03mo|·L 3)1090+109.4 Ln(NH3 1+NH31B,+[NH31B2+ B3+[ 4B4 =10321ga Zn(NH3) 3.2
9 ( ) ( ) 3 -1.5 -1 3 0.5 NH H 3 NH 0.1 NH = = = = 10 mol 0.03 1 : 0 L c 或 ( ) 3. = 3.2 H3 2 Zn N =10 lg Zn(NH3)= 1+[NH3 ]1+[NH3 ] 2 2+[NH3 ] 3 3+[NH3 ] 4 4 ( ) -1 -9.4 3 0 3 -9.0 -9.4 10 0.1 NH = NH = = 0.03 mol L 10 +10 x c
3.络合物的副反应系数ay M+Y= MY 强酸碱性溶 OH MHYM(OHY液中要考虑 计算:pH=30、50时的gmnm 查附录表I4K(ZmHY)=1030 pH=3.0,0m1)=1+1030+3.0=2,gN/≈0.3 pH=5.0, aznY()=1+10-5. 0t3. =1, 1gaznY(H=0
10 3. 络合物的副反应系数αMY M + Y = MY H+ OHMHY M(OH)Y 计算：pH=3.0、5.0时的lgαZnY(H) 强酸碱性溶 液中要考虑 查附录表III.4 K(ZnHY)=103.0 pH=3.0, αZnY(H)=1+10-3.0+3.0=2 , lgαZnY(H)= 0.3 pH=5.0, αZnY(H)=1+10-5.0+3.0=1, lgαZnY(H)= 0