titrimetric analysis

1
?27?28??
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????
????
????
????
2
?27,28??????
6-6 ?????
6-7 ?????
titrimetric analysis
6-8 ???
3
????
? ????????????,?
????,????????
????????,?????
? ??KMnO4??K2GrO7?????
?????????
4
???????
????
KMnO4??K2GrO7????????
????
???
5
6.7 ?????
6.7.1 ??
Cr2O72- 14H 6e 2Cr3 7H2O ?? 1.33 V
(1) ?????KMnO4??,??????
(2)????????????,?????????????,?????KMnO4 ???
(3)???,???????????,??????
(4)?HCl???
??HCl????????
(5)K2Cr2O7??,????,??????
6
6.7.2 ?????????
1. ????
???????????????????????
6Fe2 Cr2O72- 14H 6Fe3 2Cr3 H2O
K2Cr2O7????????KMnO4???
???? ?????(?HCl)? SnCl2( Fe3 ? Fe2 )? HgCl2 (
????? SnCl2 ) ????????
K2Cr2O7????????KMnO4???,??,??????
7
?
K2Cr2O7???HCl???????,????????,????????

• K2Cr2O7?????,?????Cr3???,????????,
• ????????(? 0'In 0.84 V)?

?????99.9?,??????
????????????????????(????),?????????,?????
8
??,???H3PO4,?Fe3(??)?PO4 3-??Fe(PO4)2
3-(??),?????Fe3???????????,?????Fe3 /
Fe2?????,???????,?????????
? ?1mol/LHCl0.25mol/L H3PO4???, ?? 'Fe3/Fe2
0.51 V, ????99.9?,??????
?????????????????,???????,?????
9
???????,????????
???????
?????HCl????????SnCl2(?????Fe3 ? Fe2
)?????? (???)?????TiCl3 (????Fe3 ? Fe2
)???????(??)(??TiCl3??W6 ? W5
)??K2Cr2O7???????????(?????TiCl3)???H2SO4H3PO4?
? ? ??????? (???) ? ?K2Cr2O7?????? ? ??(??????)
10
2. ????????(COD) ???
??????? K2Cr2O7????,???????????????
CODCr? (?GB11914-1989)
??????????H2SO4??,????K2Cr2O7??,?????????
??CO2,?????,??K2Cr2O7?FeSO4???????,???????????,???
???? 2Cr2O72- 3C 16H 4Cr3 3CO2?
8H2O 6Fe2 Cr2O72- 14H 6Fe3 2Cr3 H2O
11
6.8 ? ? ?
6.8.1 ??
6.8.1.1. ??????
????? I2????? I-????????????????
???????
I2 2e 2I -, ?0I2 /I- 0.534 V
????I2?????????,???I2???KI???,??I2?I3-?????
,????
I3- 2e 3I -, ?0I2 /I- 0.534 V
?????,??I3-???I2 ?
12
??0I2 /I- 0.534 V??, I2?????????,
I-???????????,???????,?????????????????
????????I2?????,???????????
????? I2??????????????
????????I-?????,???????????
???????? I-????????????? I2,
??????????????????( Na2S2O3 )????I2??,????????????
??
13
?????????
1. I2 / I-???????,????,???????????????????????
2.?????????,?I2????????,?????????,????????????
3.???????
6.8.1.2. ??????????
(1) I2???
(2) I - ??????????????? 4I - O2 4H
2I2 2H2O
14
???I2???,???????
? ?????KI ,?I2????????I3- ,??I2???,
KI???????????????????
? ????,?????????,??,????????????????
? ??I2???????????,??????????
15
???I - ????????????, 4I - O2 4H
2I2 2H2O ???????
? ??,????I -?????,???????,????????,
? ???????,??????I -??????
? ???????,???I2??????,????Na2S2O3??????,???????
????
16
6.8.2 ?????
????????I2?????,?????????????I2?????????,?
???????????,?S2- ? SO32- ? S2O32- ? As2O32- ?
Sn(?) ? Sb(?) ? Vc ??
I2 Red Ox 2I -
?????
???????? ?????
????????????????,???????,I2???????
3I2 6OH - IO3- 5I - 3H2O
???????, I - ??????
4I - O2 4H 2I2 2H2O
17
6.8.3 ?????
????????I-?????,???????????
??????????
???? I-????????????? I2,
Ox 2I - Red I2
????Na2S2O3?????????I2,
I2 2S2O32- S4O62- 2 I-
??????????????
????KI???????I2?????????????????,?????????
????????,???????
18
????????????????,
??
???????,I2???????
3I2 6OH - IO3- 5I - 3H2O
??, ??Na2S2O3?????????I2???SO42- ,?????????
S2O32- 4I2 10OH - 2SO42- 8I - 5H2O
???????, I - ??????
4I - O2 4H 2I2 2H2O
???????, Na2S2O3????
S2O32- 2H S? SO2 H2O
19
6.8.4 ??????????
?????????????? Na2S2O3? I2 ?
??Na2S2O3??????????
1.?????
?????Na2S2O35H2O??????,??????,??????????,
????????????,????Na2S2O3???????,????,????
?????????Na2S2O3??
Na2S2O3 Na2SO3 S?
???????CO2???(pHlt4.6)
S2O32- CO2 H2O S? HSO3- HCO3-
20
?????O2???
2S2O32- O2 2SO42- 2S?
2. ??Na2S2O3????????????
?????(?CO2???)????????
?????Na2CO3???????(??????)?
??????????,??????812?????
??????
21
3. Na2S2O3???
??Na2S2O3 ??????K2Cr2O7,KIO3???????????
???????????????,??????????KI??,???I2?Na2S2
O3????,???????,??????
Cr2O72- 6I - 14H 2Cr3 3I2 7H2O
IO3- 5I - 6H 3I2 3H2O
S2O32- I2 S4O62- 2I -
?????? ?????
22
??????????????
? KI?????,??????????
?????,??????,??????, I-??????O2??,????????0.81.0m
ol/L?
?K2Cr2O7?KI???????,???????????????????,?K2Cr2O7?KI
????,??Na2S2O3 ????? KIO3?KI???????,??????
??????????????(??????,???I2???),????????I2??????
? ?????,?????????????,????,????????,
???????(K2Cr2O7?KI???), ????????????
23
?? I2??????????
1.????I2???,?????????
????????????????I2 ,?????KI
,?????,??????,?I2????,??????,???????,??????
2.?? Na2S2O3?????As2O3???
As2O3 6OH - AsO33- 3H2O
I2 AsO33- H2O 2I - AsO43- 2H
?????, ?????? ?????
24
6.8.2 ???????
1. ???????????
???????,I2??? H2S(?????) H2S
I2 S? 2H 2I-
??H2S???,??????????,???????????????????????,?????
,?? Na2S2O3 ???????????
??????? Na2SO3? Na2S2O3??????,?????????????
?
????????????????????,??????H2S,???????????
?H2S,????????????????
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2. ????????(?????)
??????
2 Cu2 4 I -(??) 2CuI? I2 I2
2S2O32- S4O62- 2 I -
?????????????
?????????????(pH3 4),???Cu2??,?Cl-??Cu2??,???
?,????H2SO4?????
?CuI ????I2??????,?? KSCN ? CuI ????????? CuSCN
???? I2 ???,KSCN ????????, ?? SCN-?????? I2,
??????
?Fe3 ?????,???NH4HF2???????
26
3. ??????????(?????)
????????CaCl(OCl),????CaCl2?Ca(ClO3)2 ? CaO
?? ??????????(????????)???,?Cl????????
??????????? H2SO4 ???,?????KI ,????? I2 ,??
Na2S2O3 ??????,??? ClO- 2I - 2H
I2 Cl - H2O ClO2- 4I - 4H
2I2 Cl - 2H2O ClO3- 6I - 6H
3I2 Cl - 3H2O
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4. ??????
(1) ????
??????,??????????????????????,???????????
?
????????????????????,??I2????????
C6H8O6 I2 C6H6O6 2HI
???????????????????? (?????GB15347-94)
28
(2) ????
???????????,????????I2????,??????
I2 2OH- IO- I- H2O
CH2OH(CHOH)4CHO IO- OH-
CH2OH(CHOH)4COO- I-
H2O ??????IO- ,???IO3- ?I- 3IO-
IO3- 2I- ???????? I2 IO-3 5I-
6H 3I2 3H2O ???Na2S2O3?????????
I2? ???? I2 ? IO- ? CH2OH(CHOH)4CHO ,
I2 ?2Na2S2O3
29
6.10 ???????????
?1? 25.00 mL KMnO4??????????KHC2O4H2O,???
KHC2O4H2O???? 20.00 mL 0.2000 molL-1
KOH????,?KMnO4??????
?
2MnO4 - 5C2O42- 16H 2Mn2 10CO2 8H2O
KHC2O4 KOH K2C2O4 8H2O
5 c KMnO4 V KMnO4 2 c KOH V KOH
30
?2?KIO3?????????????0.1000 molL-1Na2S2O3
??????????,????? Na2S2O3 ????????25mL?? ,?????
KIO3 ????
?????
IO3- 5I - 6H 3I2 3H2O I2
2S2O32- 2I - S4O62-
m KIO3 / M KIO3 6 c Na2S2O3 V Na2S2O3
31
?3 0.1000 g????,? H2SO4 ???? 25.00 mL 0.01667
mol L-1 K2Cr2O7 ??????????,????????????,
0.1000 molL-1 (NH4)2Fe(SO4)2 ??????? K2Cr2O7 ,
?? 10.00 mL? ????????????
?
H2SO4???,?????? K2Cr2O7??
CH3OH Cr2O72- 8H CO2? 2Cr3 6H2O
Cr2O72- 6 Fe2 14H 2Cr3 6Fe3
7H2O (??)
wCH3OH / MCH3OH (c V )K2Cr2O7 - (1/6)(c V
)Fe2
32
?3 ??????0.5015g,?NaOH?????,???????250.0
mL,??25.00 mL???????,??KBrO3-KBr????25.00mL?HCl,??
???????????KI??,?????Br2????????I2,???0.1012
molL-1Na2S2O3??????,??15.05 mL???25.00 mL
KBrO3-KBr????,??HCl?KI??,???I2?0.1012
molL-1Na2S2O3??????,??40.20 mL??????????????
?
BrO3- 5Br- 6H 3Br2 3H2O
C6H5OH 3Br2 C6H2Br3OH 3HBr
Br2 2KI I2 2KBr
I2 2S2O32- 2I - S4O62-
33
????
???(P170)
?10?
??(P172-173)
?10?14?18??
34
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