11第十一章电解和库仑分析.ppt

第十一章电解和库仑分析分析法 Electrolysis and Coulometry Electrolysis and Coulometry 电解分析和库仑分析是利用将电能转变为化学能的电解池来进行的理论基础: 法拉第电解定律§11-1 电解的原理电解的原理 Principle of Principle of Electrolysis Electrolysis Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 通过称量在电解过程中,沉积于电极表面的待测物质量为基础的电分析方法。又称电重量法。此法有时也可作为离子分离的一种手段。电解分析电解分析 Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 通过测量在电解过程中,待测物发生氧化还原反应所消耗的电量为基础的电分析方法。也叫电量分析法。在100 %电流效率下电解所消耗的电量来进行定量分析的方法。库仑分析库仑分析 Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 电解分析是现有分析方法中最精密的方法之一。精确度可达千分之一。不需要标准物校正,直接获得测得量与重量的关系。电解分析常用于常量组分的分析或分离,库仑分析还可用于痕量组分的测定。特点 Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 一、电解分析基础 fundament of electrolytic analysis : 正极(阳极)负极(阴极) Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. (电解硫酸铜溶液) 当逐渐增加电压,达到一定值后,电解池中发生了如下反应: 阴极反应: Cu 2+ + 2e = Cu ?阳极反应: 2H 2 O = O 2? + 4H + +4e 电池反应: 2Cu 2+ + 2H 2 O = 2Cu + O 2 + 4H + 电池电动势为: E = - = - (V) (V) = O] [H ] ][H [O lg4 + = O) /H (O φ (V) =] lg[Cu 2 + =) (Cu/Cu φ 22 4+2 22 +2 +2与外加电压方向相反,称为反电动势(或反电压)。外加电压为