电位滴定法中终点电位的确定方法

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1、电位滴定法中终点电位的确定方法0.1mol.L-1AgNO3滴定NaClVolumeofAgNO3addedE/VV'DE/DV(V.mL-1)D2E/DV2V/mL5.00(V1)0.06210.000.00215.0(V2)0.08517.500.0042.67×10-420.0(V3)0.10721.000.0080.001122.00.12322.500.0150.004723.00.13823.250.0160.001323.500.14623.650.0500.08523.800.16123.900.0650.0624.000.17

2、424.050.090.16724.100.18324.150.110.224.200.19424.250.392.824.300.23324.350.834.424.400.31624.450.24-5.924.500.34024.550.11-1.324.600.35124.650.07-0.424.700.35824.850.050-0.125.000.37325.250.024-0.06525.500.38525.750.022-0.00426.000.39627.000.015-0.005628.000.426其中：(1)作图法求终点

3、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/mLDE/DV(V.mL-1)10.000.00217.500.00421.000.00822.500.01523.250.01623.650.05023.900

4、.06524.050.0924.150.1124.250.3924.350.8324.450.2424.550.1124.650.0724.850.05025.250.02425.750.02227.000.015V/mLD2E/DV215.02.67×10-420.00.001122.00.004723.00.001323.500.08523.800.0624.000.16724.100.224.202.824.304.424.40-5.924.50-1.324.60-0.424.70-0.125.00-0.06525.50-0.00426.

5、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xmL,则：x=0.04mL故终点体积应为24.30+0.04=24.34mL又设终点电位为E/V,从原表数据中可以看到，当二阶微商由4.4改变至-5.9时，溶液电位值由0.233V增加至0.316V，故：E=0.267V