1、4.酸碱指示剂,College of Chemistry&Chemical Engineering,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,H In,K a,HIn,In-+H+,4.1.酸碱指示剂的作用原理,College of Chemistry&Chemical Engineering,YZU,1）酸碱指示剂也是酸碱HInIn-,indicator,从结构式看出这两点,College of Chemistry&Chemical Engineering,YZU,2）酸碱指示剂颜色的变化酚酞,甲基橙,College of Chemist
2、ry&Chemical Engineering,YZU,HIn,H In,K a,College of Chemistry&Chemical Engineering,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-1 pKa+1,College of Chemistry&Chemical Engineering,YZU,指示剂,变色范围,pH,颜色变化,pKHIn,
3、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,
4、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),College of Chemistry&Chemical Engineering,YZU,甲基橙的理论与实际变色范围,College of Chemistry&Chemical Engineering,YZU,指示剂的用量温度的影响溶剂的影响滴定次序,College of Chemist
5、ry&Chemical Engineering,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,College of Chemistry&Chemical Engineering,YZU,in,KIn,H HInC a,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
6、度的影响,College of Chemistry&Chemical Engineering,YZU,T Kin 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,College of Chemistry&Chemical Engineering,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
7、法基本原理（酸碱滴定曲线）,College of Chemistry&Chemical Engineering,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,College of Chemistry&Chemical Engineering,YZU,5.酸碱滴定曲线,College of Chemistry&Chemical Engineering,YZU,强酸强碱被滴一元弱酸碱被滴多元酸碱、混合酸碱被滴C
8、O2 对酸碱滴定的影响,（一）强酸被滴以 0.1 molL 1NaOH 滴定 20.00 ml 等浓度 HCl,5.1.强酸强碱被滴,College of Chemistry&Chemical Engineering,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,20.00 V,0.1 20.00 VNaOH,H C,pH=-lgH+,College of Chemistry&Chemical Engineering,YZU,NaOH,NaOH,HCl,20.00 V,20.00 V,0.1,H C,pH=-lgH+,
9、5.1.1.计算各点溶液的 pH,College of Chemistry&Chemical Engineering,YZU,hemical Engineering,YZU,20.00 19.98,0.1 0.00005 20.00 19.98,NaOH,HCl,20.00 V,0.1 20.00 VNaOH,H C,pH=-lgH+=-lg0.00005=4.3,滴定%,NaOH,V/mL,H+,pH,0,0.00,1.010,-1,1,1.5,2.3,3.3,4.3,7,100.120.022.010-109.710120.22.010-1110.7110222.010-1211.7200
10、403.010-1College of1Che2.5mistry&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,pOH lgOH pH 14.0 pOH,V 20.00,0.1 V 20.00,OH C,5.1.1.计算各点溶液的 pH,College of Chemistry&Chemical Engineering,YZU,20.02 20.00,0.1 20.02 20.00,pOH lg 0.00005 4.3pH 14.0 4.3 9.7,OH C 0.00005,Na
11、OH,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,College of Chemistry&Chemical Engineering,YZU,V 20.00,V 20.00,OH C 0.1,pOH lgOH pH 14.0 pOHNaOH 体积为 20.02mL,5.1.2.讨论曲线形状,0,10,20,30,40,14121086420,p H,V,College of Chemistry&Chemical Engineering,YZNU aOH,VNaOH/mL,pH,0.00,1,10.00,1.5,18.00,2.3,19.80,3.3,19
12、.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,p H,V,College of Chemistry&Chemical Engineering,YZNU aOH,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,
13、7.0,4.3,p H,College of Chemistry&VChemical Engineering,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,College of Chemistry&Chemical Engineering,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,p H,V,NaOH,5.1.3.指示剂的选择,College of Chemistry&Chemical
14、Engineering,YZU,College of Chemistry&Chemical Engineering,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,College of Chemistry&Chemical Engineering,YZU,10.0,7.0,9.7,酚酞PP,甲基橙 MO,3.1,4.4,College of Chemistry&Chemical Engineering,YZU,College of Chemistry&Chemical Engineering,YZU,Col
15、lege of Chemistry&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,p H,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,College of Chemistry&Chemical Engineering,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,College of Chemistry&Chem
16、ical Engineering,YZU,0,10,2030,40,0,2,4,6,8,10,12,14,3.3,10.79.78.7,5.34.3,pH,V/mlNCoallegOe ofHChemistry&Chemical Engineering,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,p H,20V/mlNaOH,酸碱滴定的一般浓度0.1mol/L,College of Chemistry&Chemical Engineering,YZU,College of Chemi
17、stry&Chemical Engineering,YZU,以 0.1 molL 1HCl 滴定 20.00 ml 等浓度 NaOH,（二）强碱被滴,College of Chemistry&Chemical Engineering,YZU,计算各点溶液的 pH,滴定%,0,0,1.010-1,1.0,50,10,3.310-2,1.5,90,18,5.310-3,2.3,99,19.8,5.010-4,3.3,99.9,19.98,5.010-5,4.3,100,20,1.010-7,7.0,100.1,20.02,2.010-10,9.7,101,20.2,2.010-11,10.7,11
18、0,22,2.010-12,11.7,200,40,3.010-13,12.5,VHNCaOlH/mL,H+OH-,College of Chemistry&Chemical Engineering,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,p H,V,HCl,10,20,30,40,00,141210864pOH2,9.7,VNaOHHCl,College of Chemistry&Chemical Engineering,YZU,7.0,4.3,pH,
19、0,10,20,30,40,20,1210864,14,9.7,7.0,4.3,p H,V,HCl,0,10,20,30,40,14121086pOH 420,9.7,pH,0,10,20,30,40,0,24.3,47.0,6,8,10,12,14,NaOH,HCl,pH,VV,NaOHHCl,VNaOHHCl,College of Chemistry&Chemical Engineering,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,p H,V,HCl,甲基橙,7.0甲基红4.3,酚酞,College of Chemistry&Chemical Engineering,YZU,College of Chemistry&Chemical Engineering,YZU,
