酸碱滴定法-20154.pptx

酸碱滴定法-20154.pptx

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4.酸碱指示剂,CollegeofChemistry&ChemicalEngineering,YZU,酸碱指示剂的作用原理酸碱指示剂的变色范围影响酸碱指示剂变色范围的因素混合指示剂,HIn,HIn,Ka,HIn,In-+H+,4.1.酸碱指示剂的作用原理,CollegeofChemistry&ChemicalEngineering,YZU,1）酸碱指示剂也是酸碱HInIn-,indicator,从结构式看出这两点,CollegeofChemistry&ChemicalEngineering,YZU,2）酸碱指示剂颜色的变化酚酞,甲基橙,CollegeofChemistry&ChemicalEngineering,YZU,HIn,HIn,Ka,CollegeofChemistry&ChemicalEngineering,YZU,4.2.酸碱指示剂的变色范围,pH=pKa=3.4,降，,pH从3.4起下pH从3.4起上,升，,=1橙色，变色点下降，当pKa=2.4时，比值达1/10，红色上升，当pKa=4.4时，比值达10，黄色,理论变色点为pKa,理论变色范围pKa-1pKa+1,CollegeofChemistry&ChemicalEngineering,YZU,指示剂,变色范围,pH,颜色变化,pKHIn,浓度,百里酚蓝,1.22.8,红黄,1.650.1%的20%乙醇溶液,甲基黄,2.94.0,红黄,3.250.1%的90%乙醇溶液,甲基橙,3.14.4,红黄,3.450.05%的0.1%水溶液,溴酚蓝,3.04.6,黄蓝紫4.1,0.1%的20%乙醇溶液或其钠盐水,溴甲酚绿,3.85.4,黄蓝,4.9,溶0.1液%的20%乙醇溶液或其钠盐水,甲基红,4.46.2,红黄,5.0,溶0.1液%的60%乙醇溶液或其钠盐水,溴百里酚蓝,6.07.6,黄蓝,7.3,溶0.1液%的20%乙醇溶液或其钠盐水,中性红,6.88.0,红黄橙7.4,溶0.1液%的60%乙醇溶液,酚红,6.48.2,黄红,8.0,0.1%的60%乙醇溶液或其钠盐水,百里酚蓝,8.09.6,黄蓝,8.9,溶0.1液%的20%乙醇溶液,酚酞,8.09.8,无红,9.1,0.1%的90%乙醇溶液,百里酚酞,9.410.6,无蓝,10.00.1%的90%乙醇溶液,实际变色范围（p66p67）,CollegeofChemistry&ChemicalEngineering,YZU,甲基橙的理论与实际变色范围,CollegeofChemistry&ChemicalEngineering,YZU,指示剂的用量温度的影响溶剂的影响滴定次序,CollegeofChemistry&ChemicalEngineering,YZU,4.3.影响酸碱指示剂变色范围的因素,变色点pH取决于酸、碱式体浓度的比值，与CHIn无关,4.3.1指示剂的用量尽量少加，否则终点不敏锐指示剂本身为弱酸碱，多加增大滴定误差1）双色指示剂：

甲基橙,HIn,In,Kin,H,2）单色指示剂：

酚酞,a,CollegeofChemistry&ChemicalEngineering,YZU,in,KIn,HHInCa,变色点pH取决于CHIn；CHIn则pH，变色点酸移例：

50100mL溶液中加入酚酞23滴，pH=9变色1520滴，pH=8变色,4.3.2温度的影响,CollegeofChemistry&ChemicalEngineering,YZU,TKin变色范围！

注意：

如加热，须冷却后滴定,例：

甲基橙180C,3.14.42.53.7灵敏度,1000C4.3.3溶剂的影响,极性介电常数Kin变色范围4.3.4滴定次序无色有色，浅色有色例：

酸滴定碱选甲基橙碱滴定酸酚酞,4.4.混合指示剂,CollegeofChemistry&ChemicalEngineering,YZU,组成1指示剂+惰性染料例：

甲基橙+靛蓝（紫色绿色）2两种指示剂混合而成例：

溴甲酚绿+甲基红（酒红色绿色）特点变色敏锐；变色范围窄,5酸碱滴定法基本原理（酸碱滴定曲线）,CollegeofChemistry&ChemicalEngineering,YZU,强酸强碱被滴一元弱酸碱被滴多元酸碱、混合酸碱被滴CO2对酸碱滴定的影响,0,14121086420,pH,10203040VNaOH强酸被滴一元弱酸被滴多元弱酸被滴,强碱被滴一元弱碱被滴多元弱碱被滴,被强碱所滴,被强酸所滴,CollegeofChemistry&ChemicalEngineering,YZU,5.酸碱滴定曲线,CollegeofChemistry&ChemicalEngineering,YZU,强酸强碱被滴一元弱酸碱被滴多元酸碱、混合酸碱被滴CO2对酸碱滴定的影响,

（一）强酸被滴以0.1molL1NaOH滴定20.00ml等浓度HCl,5.1.强酸强碱被滴,CollegeofChemistry&ChemicalEngineering,YZU,5.1.1.计算各点溶液的pH,化学计量点前化学计量点化学计量点后,溶液为逐渐变稀的盐酸溶液,NaOH,HCl,20.00V,0.120.00VNaOH,HC,pH=-lgH+,CollegeofChemistry&ChemicalEngineering,YZU,NaOH,NaOH,HCl,20.00V,20.00V,0.1,HC,pH=-lgH+,5.1.1.计算各点溶液的pH,CollegeofChemistry&ChemicalEngineering,YZU,hemicalEngineering,YZU,20.0019.98,0.10.0000520.0019.98,NaOH,HCl,20.00V,0.120.00VNaOH,HC,pH=-lgH+=-lg0.00005=4.3,滴定%,NaOH,V/mL,H+,pH,0,0.00,1.010,-1,1,1.5,2.3,3.3,4.3,7,100.120.022.010-109.710120.22.010-1110.7110222.010-1211.7200403.010-1Collegeof1Che2.5mistry&C3,刚好中和，溶液pH=7.0,5.1.1.计算各点溶液的pH,NaOH体积为19.98mL,pH,化学计量点后，,溶液中有过剩的NaOH,NaOH,pOHlgOHpH14.0pOH,V20.00,0.1V20.00,OHC,5.1.1.计算各点溶液的pH,CollegeofChemistry&ChemicalEngineering,YZU,20.0220.00,0.120.0220.00,pOHlg0.000054.3pH14.04.39.7,OHC0.00005,NaOH,5.1.1.计算各点溶液的pH,化学计量点后，溶液中有过剩的NaOH,NaOH,CollegeofChemistry&ChemicalEngineering,YZU,V20.00,V20.00,OHC0.1,pOHlgOHpH14.0pOHNaOH体积为20.02mL,5.1.2.讨论曲线形状,0,10,20,30,40,14121086420,pH,V,CollegeofChemistry&ChemicalEngineering,YZNUaOH,VNaOH/mL,pH,0.00,1,10.00,1.5,18.00,2.3,19.80,3.3,19.98,4.3,20.00,7,20.02,9.7,20.20,10.7,22.00,11.7,40.00,12.5,0,10,20,30,40,121086420,14,pH,V,CollegeofChemistry&ChemicalEngineering,YZNUaOH,突跃范围：

化学计量点前后，规定误差范围内，pH的变化范围,Er=0.1%,VNaOH=19.9820.02ml,9.7,4.3,化学计量点pH=7.0,5.1.2.讨论曲线形状滴定突跃：

化学计量点前后，溶液pH的迅速变化,5.1.3.指示剂的选择,10,2030,40,00,1412108642,9.7,7.0,4.3,pH,CollegeofChemistry&VChemicalEngineering,YZU,NaOH,甲基红MR,4.4,6.2,4.44.3,6.2,7.0,5.1.3.指示剂的选择,CollegeofChemistry&ChemicalEngineering,YZU,4.3,4.4,6.2,7.0,甲基红变色范围（4.46.2）的全部都在突跃范围（4.39.7）内，可以使用,10,20,30,40,00,1412108642,9.7,7.0,4.3,pH,V,NaOH,5.1.3.指示剂的选择,CollegeofChemistry&ChemicalEngineering,YZU,CollegeofChemistry&ChemicalEngineering,YZU,8.0,酚酞PP10.0,7.0,9.7,酚酞变色范围（8.010.0）的一部分在突跃范围（4.39.7）内，可以使用,8.0,CollegeofChemistry&ChemicalEngineering,YZU,10.0,7.0,9.7,酚酞PP,甲基橙MO,3.1,4.4,CollegeofChemistry&ChemicalEngineering,YZU,CollegeofChemistry&ChemicalEngineering,YZU,CollegeofChemistry&Chemical,Engineering,YZU,甲基橙变色范围（3.14.4）的一部分在突跃范围（4.39.7）内，可以使用,必须特别注意颜色的变化，应当是橙黄与黄的突变，,不是橙与红的突变,10,30,40,00,1412108642,9.7,pH,20VNaOH,指示剂的选择原则是：

变色范围的全部或一部分在突跃范围内。

7.0甲基红甲4.3基橙,CollegeofChemistry&ChemicalEngineering,YZU,酚酞,5.1.3.指示剂的选择,5.1.4.滴定突跃与浓度的关系,CollegeofChemistry&ChemicalEngineering,YZU,0,10,2030,40,0,2,4,6,8,10,12,14,3.3,10.79.78.7,5.34.3,pH,V/mlNCoallegOeofHChemistry&ChemicalEngineering,YZU,1M,0.1M,0.01M,甲基橙,甲基红,酚酞,0,10,30,40,20,4,86,10,12,14,10.79.78.7,5.34.33.3,pH,20V/mlNaOH,酸碱滴定的一般浓度0.1mol/L,CollegeofChemistry&ChemicalEngineering,YZU,CollegeofChemistry&ChemicalEngineering,YZU,以0.1molL1HCl滴定20.00ml等浓度NaOH,

（二）强碱被滴,CollegeofChemistry&ChemicalEngineering,YZU,计算各点溶液的pH,滴定%,0,0,1.010-1,1.0,50,10,3.310-2,1.5,90,18,5.310-3,2.3,99,19.8,5.010-4,3.3,99.9,19.98,5.010-5,4.3,100,20,1.010-7,7.0,100.1,20.02,2.010-10,9.7,101,20.2,2.010-11,10.7,110,22,2.010-12,11.7,200,40,3.010-13,12.5,VHNCaOlH/mL,H+OH-,CollegeofChemistry&ChemicalEngineering,YZU,pHpOH,pH,13.012.511.710.79.77.04.33.32.31.5,曲线形状,0,10,20,30,40,14121086420,9.7,7.0,4.3,pH,V,HCl,10,20,30,40,00,141210864pOH2,9.7,VNaOHHCl,CollegeofChemistry&ChemicalEngineering,YZU,7.0,4.3,pH,0,10,20,30,40,20,1210864,14,9.7,7.0,4.3,pH,V,HCl,0,10,20,30,40,14121086pOH420,9.7,pH,0,10,20,30,40,0,24.3,47.0,6,8,10,12,14,NaOH,HCl,pH,VV,NaOHHCl,VNaOHHCl,CollegeofChemistry&ChemicalEngineering,YZU,指示剂的选择原则是：

变色范围的全部或一部分在突跃范围内。

10,20,30,40,00,1412108642,9.7,pH,V,HCl,甲基橙,7.0甲基红4.3,酚酞,CollegeofChemistry&ChemicalEngineering,YZU,CollegeofChemistry&ChemicalEngineering,YZU,