分析化学英文课件06沉淀滴定法 Precipitation Titration
合集下载
相关主题
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
CrO42－(yellow) + 2Ag＋ = Ag2CrO4（red）
So the concentration of the CrO42- is：
［CrO42－］=ＫspAg2CrO4 /[Ag＋]2 ＝ 5.8 × 10－2 mol/L
§6.3.2 Volhard Method
—using ferric alum as indicator
KspAgCl = [Ag+][Cl-]
§6.2 Titration Curve
For example : 0.1mol·L-1 KCl with 0.1 mol·L-1 AgNO3
(1) At the beginning of the titration pCl = 1
(2) At the equivalence point Ksp(AgCl) = [Ag+][Cl-]; [Ag+] = [Cl-] [Cl-] = (Ksp(AgCl))1/2 = 1.25×10-5 mol·L-1
( 2) Ksp: when the concentration is constant, the smaller the Ksp, the larger the break of the curve
§6.3 Detection of The End Point in Argenometry
§6.3.1 Mohr Method —using potassium chromate as indicator
be extremely low
(2) The reaction should be rapid and proceed
quantitatively
(3) Some methods must be available to detect the
end point
AgCl(s) = Ag+ + Cl-
The Volhard method is a procedure for titrating silver(Ⅰ)
with standard potassium thiocyanine.
Equations for the Volhard titration of silver are given :
So pCl = 4.90
(3) After the equivalence point [Cl-] = Ksp(AgCl) / [Ag+]
Factors influencing the titration:
(1) c : when Ksp is constant, the larger the concentration,the larger the break of the curve
titration reaction: Ag+ + X-1 = AgX(s) + excess Ag+ back-titration reaction: SCN－ + excess Ag+ = AgSCN↓ end-point reaction: Fe3+ + SCN－ = FeSCN2+
§6.3.3 Fajans Method
Argentometry
§6.1 Titratቤተ መጻሕፍቲ ባይዱons Based on
Precipitation Reactions
A precipitation reaction must satisfied the following
requirements before it can be used:
(1) The solubility of the produced precipitate should
Ag＋ + SCN－ = AgSCN↓
(titration reaction)
Fe3＋ + SCN－ = FeSCN2＋
(end-point reaction)
(1) The titration is carried out in acid solution.
(2) This method can be used to determine chloride and other anions.
Analytical Chemistry 分析化学
Chapter 6 Precipitation Titration
§6.1 Titrations Based in Precipitation Reactions
§6.2 Titration Curve §6.3 Detection of the End Point in
—using adsorption indicator
In the adsorption indicator method for halide
ions, the end point reactions occurs on the surface of the silver halide precipitate.
The adsorption indicators are some colored organic compounds. Fluorescein is a kind of adsorption indicator. It can be adsorbed on the surface of the colloidal particles and change color.
(1) This method can be used to determine the chloride ,
and the standard solution is AgNO3.
Reactions: Ag＋ + Cl－ = AgCl At the equivalence point ：
［Ag＋］= (ＫspAgCl )1/2 = 1.25×10－５
So the concentration of the CrO42- is：
［CrO42－］=ＫspAg2CrO4 /[Ag＋]2 ＝ 5.8 × 10－2 mol/L
§6.3.2 Volhard Method
—using ferric alum as indicator
KspAgCl = [Ag+][Cl-]
§6.2 Titration Curve
For example : 0.1mol·L-1 KCl with 0.1 mol·L-1 AgNO3
(1) At the beginning of the titration pCl = 1
(2) At the equivalence point Ksp(AgCl) = [Ag+][Cl-]; [Ag+] = [Cl-] [Cl-] = (Ksp(AgCl))1/2 = 1.25×10-5 mol·L-1
( 2) Ksp: when the concentration is constant, the smaller the Ksp, the larger the break of the curve
§6.3 Detection of The End Point in Argenometry
§6.3.1 Mohr Method —using potassium chromate as indicator
be extremely low
(2) The reaction should be rapid and proceed
quantitatively
(3) Some methods must be available to detect the
end point
AgCl(s) = Ag+ + Cl-
The Volhard method is a procedure for titrating silver(Ⅰ)
with standard potassium thiocyanine.
Equations for the Volhard titration of silver are given :
So pCl = 4.90
(3) After the equivalence point [Cl-] = Ksp(AgCl) / [Ag+]
Factors influencing the titration:
(1) c : when Ksp is constant, the larger the concentration,the larger the break of the curve
titration reaction: Ag+ + X-1 = AgX(s) + excess Ag+ back-titration reaction: SCN－ + excess Ag+ = AgSCN↓ end-point reaction: Fe3+ + SCN－ = FeSCN2+
§6.3.3 Fajans Method
Argentometry
§6.1 Titratቤተ መጻሕፍቲ ባይዱons Based on
Precipitation Reactions
A precipitation reaction must satisfied the following
requirements before it can be used:
(1) The solubility of the produced precipitate should
Ag＋ + SCN－ = AgSCN↓
(titration reaction)
Fe3＋ + SCN－ = FeSCN2＋
(end-point reaction)
(1) The titration is carried out in acid solution.
(2) This method can be used to determine chloride and other anions.
Analytical Chemistry 分析化学
Chapter 6 Precipitation Titration
§6.1 Titrations Based in Precipitation Reactions
§6.2 Titration Curve §6.3 Detection of the End Point in
—using adsorption indicator
In the adsorption indicator method for halide
ions, the end point reactions occurs on the surface of the silver halide precipitate.
The adsorption indicators are some colored organic compounds. Fluorescein is a kind of adsorption indicator. It can be adsorbed on the surface of the colloidal particles and change color.
(1) This method can be used to determine the chloride ,
and the standard solution is AgNO3.
Reactions: Ag＋ + Cl－ = AgCl At the equivalence point ：
［Ag＋］= (ＫspAgCl )1/2 = 1.25×10－５