沉淀滴定与重量分析分析.ppt

;Contents;微溶化合物的溶解度和溶度积 Solubility and solubility product constant;1. Solubility (s) and solubility product constant (Ksp);1.1 Solubility (s) and solubility product ;solubility product constant and conditional solubility product constant;Table Several Solubility Product Constants at 25°C;Question ;Question ;1.2 Factors which affect s;(2) The Common-Ion Effect in Solubility Equilibrium 同离子效应;The Common-Ion Effect;沉淀重量法总要加过量沉淀剂.;;(3). Acidic Effects －Increase s;在pH=1.0的酸性溶液中;若pH=4.0，过量H2C2O4 ( c=0.10mol·L-1) ; Ag2S =2Ag++S2－ 2S S/as(H);∵　Ksp较大, S2-定量成为HS-, 产生同量OH- ∴假设 MnS+H2O=Mn2++HS－+OH－ S S S;检验：[OH-]=S=10-4.6 mol·L-1, [H+]=10-9.4 mol·L-1 ?S(H)＝1＋10-9.4+12.9+10-18.8+20.0 ＝1 + 103.5 + 101.2＝103.5 S2- HS- H2S 主要以HS-存在 故假设合理。;S最小;H+;Ksp′=Ksp? Pb(Y)? C2O4(H) =10-9.7+7.4+0.3=10-2.0;(5). 影响s 的其他因素;2. 沉淀滴定 Precipitation Titration;沉淀反应为基础的分析方法;Precipitation Titration Curve;SP pCl = pAg = 1/2 pKsp = 4.91;Taking account of the dissolution of the precipitation -0.1% [Cl-] =[Cl-]sur+[Cl-]sol [Cl-]sol=[Ag+]=a Ksp=[Cl-][Ag+]=([Cl-]sur+a)a a= 2.9 ? 10-6 mol/L, pCl = 4.28, pAg = pKsp - pCl = 9.81 - 4.28 = 5.53;;End-Point Detection;Experimental dosage： 5.2-2.6 ? 10-3 mol/L , ;用0.1000 mol/L Ag+ 滴定0.1000 mol/L KCl, 指示剂[CrO42-]= 5.00×10-3 mol/L。计算由指示剂引入的终点误差。(生成可判断终点的AgCrO4需消耗2.00×10-5 mol/L的Ag+);总多消耗的Ag+: [Ag+]总=0.43×10-5+2.00×10-5= 2.43×10-5mol/L 终点误差：;Acidity of solutions Acidity：pH 6.5 ~ 10.5；pH 6.5 ~7.2 when NH3 exist Strong acid： H++CrO4 Cr2O72- (K=4.3×1014) Strong base： Ag2O precipitation;b. Volhard (NH4Fe(SO4)2 as indicator) i). Direct titration (determining Ag+) Titration reaction: Ag++SCN- ?AgSCN(s) white Indication reaction: Fe3++ SCN- ?FeSCN2+(s) red Something Notable: Acidity of solutions (0.3 mol/L HNO3 ) Concentration of indicator (1-2 ml 40%) Interference of adsorption ;b. Volhard ii). Back titration