第七章 氧化还原滴定法 氧化还原滴定法（ Redox Titration...

Redox Titration

7-1 E0251mol/L11.013105Pa

Ox + ne- = Red E E = E0 OX/Red + (0.059/n)lg[OX]/[Red] 1 [Ox]=[Red]=1mol/Llg[OX]/[Red] =0E=E0

1E E0 H+

1 E=E 0 OX/Red+(0.059/n)lgaOX/aRed 2OxRedn1mol2

E=E0OX/Red+(0.059/n)lgOXcOXRed/RedcRedOX (3) EoOX/Red=E0OX/Red+(0.059/n)lgOXRed/Red OX (4) E=EoOX/Red+(0.059/n)lgcOX/cRed 4conditional potential1molL-1 KK

EoE0

7-1 1mol/LHCl,cCe(IV)=1.0010-2 mol/L, cCe(III)=1.0010-3mol/L Ce(IV)/Ce(III)11Ce(IV)+e-=Ce(III)1mol/LHClEo=1.28V E = EoCe(IV)/Ce(III) + 0.059lg[cCe(IV)/cCe(III)] = 1.28V+0.059lg1.0010-2/1.0010-3 = 1.34V

7-2 2.5mol/LHCl0.100mol/LK2Cr2O7Cr2O72-/Cr3+Cr2O72-+14H++6e-=2Cr3++7H2O 113mol/LEoEo=1.08V0.100mol/LK2Cr2O7 cCr(VI) = 0.50.100mol/L=0.0500mol/L cCr(III)=20.0500mol/L=0.100mol/L E = EoCe(VI)/Cr(III) + (0.059/6)lgcCr(VI)/c2Cr(III) = 1.08+(0.059/6)lg0.0500/(0.100)2 = 1.09V

()

E0Sn2+/Sn = -0.14VE0Pb2+/Pb = -0.13V[Sn2+]=[Pb2+]=1mol/LPb2+SnPb2++SnSn2++Pb [Sn2+] = 1.0mol/L[Pb2+] = 0.10 mol/L ESn2+/Sn = - 0.14 + 0.059/2log(1) = - 0.14V EPb2+/Pb = - 0.13 + 0.059/2log(0.1) = - 0.16VESn2+/Sn >EPb2+/Pb,Sn2+Pb Sn2++PbPb2++Sn

E (Eo)E00.01Pb2+10E0(Eo)

SnCu2+CuCu2+ + Sn Cu + Sn2+ E0Cu2+/Cu= + 0.34E0Sn2+/Sn= - 0.140.48Cu2+1.010-17mol/L

,,,,1

,,Cu2+Cu2+ + 4I- = 2CuI + I2 E0 Cu2+/Cu+=0.16V E0I2/I-=0.54VI2Cu+Cu2+I-Cu+CuI

,(E),,, KMnO4 K2Cr2O7(NH4)2S2O8

H+H+ 1H+ H+OH E0(Eo) H3AsO4+2I-+2H+=H3AsO3+I2+H2O[H+]=1.0mol/L

2H+ H+ Fe(CN)63+e=Fe(CN)64 E0=0.356V H+pH4HFe(CN)63 pH4Fe(CN)63Fe(CN)64H+EpH4H+

K aOx1+bRed2 = cRed1+dOx2lgK=lgccRed1cdOX2/caOX1cbRed2=n(Eo1- Eo2 )/0.059 E1oE2on

KE1oE2oKE1oE2oKOx1Red2aOx1+bRed2=aRed1+bOx2 0.1%99.9 [Ox2]99.9CRed2, [Redl]99.9COx10.1% [Red2]0.1CRed2 [Ox1]0.1COx1

lgKlg(103)a+b nE/0.0593(a+b) E3(a+b)0.059/n n1=n2=1, , a=b=1, n=1lgK6, E0.35V n1=2,n2=1,, a=1,b=2,n=2, lgK9, E0.27V n1=1,n2=3,, a=3,b=1,n=3, lgK12, E0.24V n1=n2=2, , a=b=1, n=2, lgK6, E0.18V n1=2,n2=3,, a=3,b=2,n=6, lgK15, E0.15V 0.4()0.4

()KMnO4Na3AsO3(H2SO4)(0.95)0.4AsO33-MnO4-3.3Mn()

72 KH2O2K1041()

H2O2I H2O2+ I+2H+=I2+2H2O 111 H2O2+ I=IO+H2O 2 IO+H+=HIO 3 HIO+H++I=I2+H2O 4

102470-80

I2I2Sn2+Fe2+

Na2C2O4KMnO42MnO4+5C2O42+16H+=2Mn2++10CO2+8H2O

Mn2+ Mn()+Mn()Mn()+Mn() Mn() 2Mn() Mn() 2Mn()() Mn()C2O42,MnC2O4+()Mn(C2O4)2-()Mn(C2O4)32- ()Mn()CO2 MnC2O4+Mn2++ CO2+COO- Mn()+COOMn2++ CO2

Mn2+MnO4Mn2+

KMnO4Cl-Fe2+MnO4-Fe2+MnO4-Cl-MnO4-Fe2+MnO4-Cl- MnO4-+5Fe2++8H+Mn2++5Fe3++4H2O () 2MnO4-+10Cl-+16H+2Mn2++5Cl2+8H2O ()MnO4-Fe2+Cl-

7-3 pH

c0Ox1Ox1c0Red2V0Red2aOx1+bRed2=aRed1+bOx2VOx1f=bc0(Ox1)V/ac0(Red2)V0fsp=1, c0 (Ox1)Vsp/c0(Red2)V0=a/bf

0.1000mol/LCe(SO4)220.000.1000mol/LFe2+1mol/LH2SO4 Fe3++e=Fe2+ EoFe3+/Fe2+=0.68V Ce4++e=Ce3+ EoCe4+/Ce3+=1.44VCe4+Fe2+ Ce4+ + Fe2+ = Ce3+ + Fe3+

0.1000mol/LFe2+Fe3+Fe3+/Fe2+Fe3+

Fe3+/Fe2+Ce4+/Ce3+: E=Eo Fe3+/Fe2++0.059lgCFe3+ /CFe2+ E=Eo Ce4+/Ce3+ +0.059lgCCe4+ /CCe3+ Ce4+Fe3+/Fe2+ECe4+10.00mLf=0.5cFe3+=cCe3+=0.110.00/(20.00+10.00) cFe2+=0.110.00/(20.00+10.00) E=0.68VCe4+19.98mLf=0.999 E=0.86V

20.00mL 0.10mol/L Ce4+f=1 EFe3+/Fe2+=ECe4+/Ce3+ =Esp Esp=0.68+0.059lgC Fe3+ /C Fe2+ Esp=1.44 +0.059lgCCe4+/CCe3+ 2 Esp= 2.12+0.059lgC Fe3+ /C Fe2+ +0.059lgCCe4+/CCe3+ CCe4+=CFe2+ CCe3+=CFe3+ Esp=1.06V

Ce4+Ce3+

Ce4+ V/ml f/% E/V 1.00 5.00 0.60 10.00 50.00 0.68 18.00 90.00 0.74 19.80 99.00 0.80 19.98 99.90 0.86 20.00 100.0 1.06 20.02 100.1 1.26 22.00 110.0 1.32 30.00 150.0 1.42 40.00 200.0 1.44

Fe2+0.1Ce4+0.1%1.26-0.860.40

() ()0.200.200.400.40()

Ce4+Fe2+Esp() n1=n2n1n2(n)n1n2

KMnO4Fe2+ 1. Eo2EoFe3+/Fe2+Eo2Fe3+PO43Fe3+[Fe(HPO4)]+Fe3+Fe2+0.5mol/LHC1Eo2+0.7l2mol/LH3PO4Eo20.46H3PO4HClFe2+0.46Ce(SO4)2KMnO4K2Cr2O7Fe2+H3PO4HCl

0.1000mol/L KMnO4Fe2+A-1mol/LHClO4B-0.5mol/L H2SO4C-1mol/L HCl + 0.25mol/L H3PO4

2. EoMn()/Mn()Mn()PO43SO42ClO4-HClO4KMnO4Fe2+,

n2Ox1 + n1Red2 = n2Red1 + n1Ox2 Esp= (n1Eo1+ n2Eo2)/( n1+n2) E1oE2on1 n 2(E0)

0.1%

7-4 , In(Ox)In(Red)nH+ In(Ox) + ne = In(Red)

EIn = EIno + 0.059/n lgCIn(Ox)/CIn(Red) (1) EInoEInoIn(Ox)In(Red)CIn(Ox)/CIn(Red)10/11/10(A) EIn = EIno 0.059/n 25 (2) EInoIn(Ox)In(Red)(EIn)EIno

Fe2+ () Ce4+Fe2+0.85(H+1mol/L)Ce4+()() EIn=0.850.059/2=0.850.03() 0.82-0.88()

()Fe(II) C12H8N2FeC12H8N232+ Fe(C12H8N2)32+ - e = Fe(C12H8N2)33+ () () Fe(C12H8N2)33+,1mol/LH2SO4,EIno1.061.12,()()Ce4+Fe2+,Fe(II)Fe2+ Ce4+()

() (I3)(I22105mol/L)

() KMnO4MnO4 KMnO42106mol/L(0.2mol/L)MnO48107mol/L

0.01mol/L

7-5 ,,

Fe3+Fe2+Fe2+SnCl2 2Fe3+ + SnCl2 + 4C1 2Fe2+ + SnCl62KMnO4K2Cr2O7Ce4+KMnO4 MnO4 + 5Fe2+ + 8H+ Mn2+ + 5Fe3+ + 4H2O

SnCl2Fe3+ (1) SnCl2HgCl2 Sn2++HgC12+4C1SnCl62 +Hg2C12 () (2) Hg2C12Hg2C12KMnO4(K2Cr2O7) 5Hg2Cl2+2MnO4+16H+=10Hg2++10Cl+2Mn2++8H2O Hg2Cl2SnCl2SnCl2FeCl412SnCl2Fe2+

(3) Hg2C12Hg Hg2C12+Sn2++4C12HgSnCl62 KMnO4 10Hg+2MnO4+16H++10C1 5Hg2C12+2Mn2++8H2O HgCl2SnCl2HgC12

(4) Hg2C12Fe3+ Hg2C12+2FeCl42Hg2++2Fe2++10C1Fe2+ p2217374

7-6 KMnO4 MnO4- + 8H+ + 5e- Mn2+ + 4H2O E01.51V ,(MnO2H2O)KMnO4H2SO4HClHNO3C1-MnO4-HNO3

KMnO4 () FeSO4H2C2O4H2O2 Sn2+Ti(III)Sb(III)As(III)NO2KMnO4 () KMnO4

MnO2H2SO4Na2C2O4 ()Na2C2O4MnO2C2O42-KMnO4C2O42-MnO2Na2C2O4MnO2 KMnO4

() KMnO4Ca2+Ca2+CaC2O4H2SO4CaC2O4KMnO4C2O42-Ca2+ KMnO4

() H2O2 KMnO4H2O2 MnO4- + 5 H2O2 + 6H+ = 2Mn2+ + 5O2+ 8H2O Mn2+Mn2+ FeSO4As()Sb()H2C2O4Sn2+NO22-

() Ca2+Ca2+C2O42-CaC2O4CaC2O4H2SO4KMnO4 Ca2++C2O42-CaC2O4 () CaC2O4+2H+Ca2++H2C2O4 5H2C2O4+2MnO4-+6H2Mn2++10CO2+8H2O C2O42-KMnO4

()MnO2 MnO2MnO2MnO2Na2C2O4KMnO4C2O42- MnO2 + C2O42- + 4H+ 2Mn2+ + 2CO2+ 2H2O

() 6MnO4-+CH3OH+8OH-=CO32-+6MnO42-+6H2O MnO42-MnO4-MnO2FeSO4Mn2+KMnO4Fe2+

K2Cr2O7Cr3+ Cr2O72- + 14H+ + 6e- 2Cr3+ + 7H2O K2Cr2O7 K2Cr2O7(E01.33V)KMnO4(E01.51V)

1.K2Cr2O7140150 2.K2Cr2O7, 3.K2Cr2O7KMnO41mol/LHClEo1.00VC1-(E0Cl2/Cl-1.33)HClFe2+HClK2Cr2O7C1- K2Cr2O7

1. HClHClSnCl2Fe(III)Fe(II)SnCl2HgCl2Hg2C121-2mol/LH2SO4 -H3PO4K2Cr2O7Fe(II) SnCl2+2HgCl2= SnCl4+2Hg2Cl2 Cr2O72-+6Fe2++14H+=2Cr3-+6Fe3++7H2O

2. (COD)O2

3. H2SO4K2Cr2O7(170180)K2Cr2O7CO2K2Cr2O7(NH4)2Fe(SO4)2Cr2O72-+8H++CH3OH2Cr3++CO2+6H2OCr2O72-+6Fe2++14H+2Cr3++6Fe3++7H2O

() I2I-I2+2e-=2I- E0I2/I-=0.535V E0I2I- 1. () E0I2/I-I2S2-SO32-Sn2+S2O32-AsO32-SbO33-

2. () E0I2/I-Na2S2O3I2K2Cr2O7KII2Na2S2O3 Cr2O72-+6I-+14H+2Cr3++3I2+7H2O I2+2S2O32-2I-+S4O62-,ClO3-ClO-CrO42-IO3-BrO3-SbO43-MnO4-MnO2 AsO43-NO3-NO2-Cu2+H2O2CrO42-Pb2+Ba2+

5106mol/L(5025110)5050III2110-5 mol/LI-210-5 mol/L pH2I2pH9I2IO-

I2I- I2 1. KIKII2I3I2I2 KI 2. I2Na2S2O3Na2S2O3 3.

I- 1. I-,Na2S2O3 2.pH S2O32-I2I2S2O32- S2O32-+4I2+10 OH-2SO42-+8I-5H2O I2 3 I2+6OH-IO3-+5I-+3H2O

Na2S2O3 S2O32-+2H+SO2+S+ H2O I-O2 4I-+4H++O2=2I2+2H2O 3.Na2S2O3(I2-)

1. HClHNO3NH4HF2Fe3+FeF63-pH3.54.0KICu2+I2Na2S2O3 2Cu2++4I-2CuI+I2 I22S2O32-2I-+S4O62- 0.5%

2. HAcNaAcCrO42-Ba2+BaCrO4HClKICr2O72-I-I2I2Na2S2O3 Ba2++ CrO42-BaCrO4 () 2BaCrO4+4H+2 Ba2++H2Cr2O7+H2O Cr2O72-+6I-+14H+3I2+Cr3++7H2O I2+2S2O32-2I+S4O62-

3. I2OH-IO- I2+2OH-=IO-+I-+H2O CH2OH(CHOH)4CHO+IO-+OH-= CH2OH(CHOH)4COO-+I-+H2O IO- 3IO-= IO3-+ I- I2 IO3-+5I-+6H+=3I2+H2ONa2S2O3 2S2O3+I2=2S4O62-+2I-

4. S2-H2SI2H2SH2S+I2 = S+2I-+2H+ SSO2H2SO3I2H2SO3 SO2+H2O=H2SO3 I2+H2SO3+H2O= 2I-+SO42-+4H+

Ce(SO4)2Ce4+ Ce4+Ce4+Ce3+ Ce4++e-Ce3+ E0=1.61V Ce4+/Ce3+HClO4Ce4+ClO4-Ce4+(C1-SO42-)Ce(SO4)2HClO4H 2SO4

Ce(SO4)2KMnO4 1. 2. ()Fe2+ 3. HClCe4+Fe2+ (KMnO4) Ce4++ Fe2+Fe3++Ce3+ C1-Ce4+Ce4+Fe2+Cl 4. Ce(SO4)2 5. Ce(SO4)2(NH4)2SO42H2O

(1mol/L)Ce(SO4)2KMnO4Ce(SO4)2() Ce4+Ce4+Ce3+Ce4+Fe()

KBrO3 KBrO3KBrO3KBrO3Br- BrO3-+6H++6e-Br-+3H2O E0=1.44V KBrO3180KBrO3 KBrO3KI BrO3-+6I-+6H+=Br-+3I2+3H2OI2Na2S2O3KBrO3

KBrO3KBrO3KBrBrO3-Br- BrO3-+5Br-+6H+3Br2+3H2O Br2Br2 KBrO3KBrKBrO3KBrBr2Br2 PhOH+3Br2=PhBr3OH+3H++3Br- KIBr2I2Na2S2O3

7-7

7-7 Pb3O40.1000gPb2+K2CrO4Pb2+PbCrO4KI0.1000mol/L Na2S2O3I213.00mLPb3O4

Pb2+Pb3O4+2Cl-+8H+=3Pb2++Cl2+4H2OPb2++CrO42-=PbCrO42PbCrO4+2H+=2Pb2++Cr2O72-+H2OCr2O72-+6I-+14H+=2Cr3++3I2+7H2O2S2O32-+I2=2I-+S4O62- 2Pb3O46Pb2+6CrO42-3Cr2O72-9I218S2O32- Pb3O49S2O32-

wPb3O4=[(1/9cNa2S2O3VNa2S2O3MPb3O4)/ms]100% =[(1/90.1000mol/L13.0010-3L 685.6g/mol)/0.1000g]100% =99.03%

7-8 0.5000g0.7500g H2C2O42H2OH2SO430.00mL0.0200mol/LKMnO4wMnO2 MnO2 MnO2+H2C2O4+2H+=Mn2++2CO2+2H2O 2MnO4-+5H2C2O4+6H+=2Mn2++10CO2+8H2O

: 5MnO25H2C2O42MnO4-MnO2 wMnO2={[(mH2C2O42H2O/MH2C2O42H2O- 5/2cKMnO4VKMnO4)MMnO2]/ms}100% ={[(0.75/126.07-5/20.0200030.00 10-3)86.94]/0.5000}100% =77.36%

7-9 25.00mL KIHCl10.00ml0.0500mol/LKIO3I2KIKIO3I20.1008mol/L Na2S2O421.14mL: IO3-+5I-+6H+=3I2+3H2O I2+2S2O32-=S4O62-+2I-

IO3-5I- IO3-3I26S2O32-KIKIO3 cKIO3VKIO3 - 1/6cNa2S2O3VNa2S2O3 cKI=[(cKIO3VKIO3-1/6cNa2S2O3VNa2S2O3)5]/VKI =[(0.050010.0010-3-1/60.1008 21.1410-3)5]/25.0010-3 = 0.02896mol/L