电位滴定法中终点电位的确定方法.doc

电位滴定法中终点电位的确定方法0.1mol.L-1AgNO3 滴定NaClVolume of AgNO3 addedE/VVD E/ D V(V.mL-1)D 2E/ D V2V/mL5.00(V1) 0.06210.000.00215.0(V2)0.08517.500.0042.6710-420.0(V3)0.10721.000.0080.001122.00.12322.500.0150.004723.00.13823.250.0160.001323.500.14623.650.0500.08523.800.16123.900.0650.0624.000.17424.050.090.16724.100.18324.150.110.224.200.19424.250.392.824.300.23324.350.834.424.400.31624.450.24-5.924.500.34024.550.11-1.324.600.35124.650.07-0.424.700.35824.850.050-0.125.000.37325.250.024-0.06525.500.38525.750.022-0.00426.000.39627.000.015-0.005628.000.426 其中：(1) 作图法求终点V/mLE/V5.000.06215.00.08520.00.10722.00.12323.00.13823.500.14623.800.16124.000.17424.100.18324.200.19424.300.23324.400.31624.500.34024.600.35124.700.35825.000.37325.500.38526.000.39628.000.426V/mLD E/ D V(V.mL-1)10.000.00217.500.00421.000.00822.500.01523.250.01623.650.05023.900.06524.050.0924.150.1124.250.3924.350.8324.450.2424.550.1124.650.0724.850.05025.250.02425.750.02227.000.015V/mLD 2E/ D V215.02.6710-420.00.001122.00.004723.00.001323.500.08523.800.0624.000.16724.100.224.202.824.304.424.40-5.924.50-1.324.60-0.424.70-0.125.00-0.06525.50-0.00426.00-0.0056（2）二阶微商法（代数法）确定终点根据代数学原理，在终点体积时，二阶微商为零，从上图中可以看出，当滴定体积个24.30增加至24.40时，二阶微商由正值变为负值，表明终点体积应介于24.30mL 24.40mL之间。因此可以通过下面的比例方程求得终点体积：设当二阶微商由4.4减小至0时，滴定体积增加了x mL, 则：x = 0.04mL故终点体积应为 24.30 + 0.04 = 24.34 mL又设终点电位