文档介绍：Chapter 6
PrecipitationPrecipitation TitrationTitration
AndAnd
GravimetryGravimetry (Gravimetric(Gravimetric Method)Method)
VOCABULARY
Precipitation titration 沉淀滴定 Solubility 溶解度
Gravimetric method 重量法 Precipitant 沉淀剂
Degree of Supersaturation 过饱和和度
Nucleation 成核作用 Colloidal 胶体(or sol)
(conditional) solubility product ((条件条件))溶度积溶度积
Argentometry 银量法 Surface adsorption 表面吸吸附
Adsorption indicator 吸吸附指示剂 Coprecipitation 共沉淀
Postprecipitation 后沉淀 Occlusion 包藏
Common ion effect 同离子效应 Salt effect 盐效应
Amorphous 无定形 Crystalline 结晶
Homogenous percipitation 均匀沉淀 Diffusion layer 扩散层
§§ PrecipitationPrecipitation TitrationTitration
§§ IntroductionIntroduction ofof GravimetryGravimetry
§ PrecipitationPrecipitation Solubility
§§ PrecipitationPrecipitation puritypurity
Precipitation Titration
Ag + + X - = AgX ↓
Detect: Cl -、Br -、I-、SCN -
and Ag +
1 Titration curve
3 titrate :
before sp :(%)
− −−
[Cl ]= × = 5 × 105 = 10
+
−10
+ K × 10 −
[Ag ]=sp = = 10
[Cl −] 5× 10 − 5
pAg =
:
+= −= = −
[Ag ] [ Cl ] K sp 10
3. after sp : (+%)
+ −−
[Ag ]= × = 5 × 105 = 10
+
pAg =
Titration Curve
10
AgNO
8 3
6 NaCl
pAg 4
2 ·L-1
1mol·L-1
0
0 50 100 150 200 T/ %
AgNO 3
16
5
.
2
1
- - -
Cl Br I
12
-1
(1mol·L )
8
.
8
pAg
8
2
.
6
3
3 3
.
. .
3
4 3 3
0
0 50 100 150 200
T/%
1 Mohr method :
K2CrO 4: as indicator ;
AgNO 3 :standard solution ;
Detect:Cl - Br -;Acidity : pH=-
- + -10
Cl 被测+Ag =AgCl ↓ Ksp = ×10
= = × −5
S K sp 10 mol / L
2- + -12
CrO 4 =2Ag =Ag 2CrO 4↓ Ksp = ×10
3 K
S=sp = × 10−4 mo