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第三节 PowerPoint PPT Presentation


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第三节. 络合滴定中的副反应 和条件形成常数. 上一节我们讨论了简单络合物平衡体系中有关各型体浓度的计算。实际上,在络合滴定过程中,遇到的是比较复杂的络合平衡体系。在一定条件和一定反应组分比下,络合平衡不仅要受到温度和该溶液离子强度的影响,而且也与某些离子和分子的存在有关,这些离子和分子,往往要干扰主反应的进行,以致使反应物和反应产物的平衡浓度降低。. 一、络合滴定中的副反应和副反应系数.

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第三节

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4354051


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()H+OH-pHMYMY


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() YY

1. EDTAY(H)

H+Y4-H+YpH

Y(H)


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(1) Y(H)

[Y]M()EDTA[Y]Y[Y]

YYY(H)


2 y h

(2) Y(H)

Y(H)[H+]H+ Y(H)[Y]


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[Y]=[Y]+ [HY] +[H2Y] + [H3Y] + [H4Y] + [H5Y] + [H6Y]

[Y]=[Y]+1H[Y][H+] + 2H[Y][H+]2 ++ 6H[Y][H+]6

Y(H)=1+ 1H[H+]+ 2H[H+]2++ 6H [H+]6

  • =1+iH[H+]i


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  • : pH5.00EDTAY(H)lgY(H)

  • EDTA

  • lg1Hlg6H10.2616.4219.0921.0922.6923.59


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EDTAlg1Hlg6H10.2616.4219.0921.0922.6923.59

  • [H+]=10-5.00mol.L-1

  • Y(H)=1+ 1H[H+] + 2H[H+]2++ 6H[H+]6

  • Y(H) =1+1010.2610-5.00+1016.4210-10.00+1019.0910-15.00

  • +1021.0910-20.00+1022.6910-25.00+1023.5910-30.00

  • =1+105.26+106.42+104.09+101.09+10-2.31+10-6.41

  • =106.45

  • lgY(H)=6.45

(1)

(2)4(p346)pHlgY(H)


2 edta y n

2. EDTAY(N)

EDTANMNEDTANMEDYA

:(1)N[N]

(2)NYN


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  • N1N2NnM Y(N)

  • Y(N)= Y(N1)+ Y(N2) + + Y(Nn) -(n-1)


3 edta

3. EDTA

()

:[Y]=[Y]+[HY]+[H2Y]+[H3Y]++[H6Y] +[NY]

H+NY


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  • EDTAPb2+(1)Ca2+, (2)Mg2+0.010mol.L-1pH=5.0EDTAPb2+ Y lgY

  • KPbY=1018.04, KCaY=1010.7, KMgY=108.7


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: EDTAPb2+

4pH=5.0lgY(H)=6.45

KPbY=1018.04, KCaY=1010.7,KMgY=108.7EDTAPb2CaY[Ca2+]0.010mol.L-1=10-2.00 mol.L-1 [Mg2+]0.010mol.L-1=10-2.00 mol.L-1


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Y(N)=1+KNY[N]

(1) Y(Ca)=1+KCaY[Ca2+]=1+1010.710-2.00=108.7

Y= Y(H)+ Y(N) -1

Y= Y(H)+ Y(Ca)-1=106.45+108.7-1108.7

lgY=8.7

(2) Y(Mg)=1+KMgY[Mg2+]=1+108.710-2.00=106.7

Y= Y(H)+ Y(Mg)-1=106.45+106.7-1106.9

lgY=6.9

100


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()MM

  • 1. MM(L)

  • M

  • M(L)

(1) M(L)[L]

(2) [L] M(L)M[M]


2 m m oh

2MM(OH)


3 m m

3. MM

  • MLOH-


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0.10mol.L-1 NH30.18 mol.L-1NH4+ ()Zn

pH10.0Zn()

  • lg1 lg42.27,4.61,7.01,9.06 pKa(NH4+)=9.26


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lg1 lg42.27,4.61,7.01,9.06;

[NH3]=10-1.00 mol.L-1, pKa(NH4+)=9.26

  • (1)6pH=9.0lgZn(OH)=0.2


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  • 3[NH3]34[NH4]4Zn(NH3)32+Zn(NH3)42+

pH=10.0lgZn(OH)=2.4

NH3KH=109.26


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[NH3]NH3Zn2+Zn2+Zn

pH=11.0, =5.4


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MY

pH3MHY

pH11,MOHY


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MY


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(1)

MYKMY

M + Y = MY


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(2)

KMY


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MY,

KMY:

KMY


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(1)

(2)pH12.0lgY(H)=0

(3)pH12.0


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  • pH12 Y(H)=1

  • MY

  • MY


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  • NH3-NH4+pH =10.0EDTAZn2+[NH3]=0.10molL-1, [CN-]=1.010-3molL-1logKZnY

  • lgKZnY=16.50 ,

  • NH3KH=109.26

  • pH =10.0 lgY(H)=0.45, lgZn(OH)=2.4

    lg1 lg42.27,4.61,7.01,9.06;

    Zn2+-CN-lg4=16.7


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  • (1) pH =10.0lgZn(OH)=2.4

  • [NH3]=0.10molL-1

    lg1 lg42.27,4.61,7.01,9.06

Zn2+-CN-lg4=16.7


Ph 10 0 lg y h 0 45

pH =10.0 lgY(H)=0.45,


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