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1、第四章 沉淀溶解平衡Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.一、难溶电解质的溶度积和溶度积规则1 溶度积常数 1) 物质的溶解度：溶解度小于0.01(克/100克水）的物质称 为难
2、溶物质；溶解度在0.01(克/100克水）至0.1 (克 /100克水）之间的物质称为微溶物质；溶解度较大的称为易溶物质。Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.2) 溶度积常数沉
3、淀-溶解平衡是当溶解和结晶速度相等时建立的平衡，是一种动态平衡。AgCl(s) Ag+ + Cl-此时的溶液是饱和溶液。其平衡关系为：Ksp(AgCl) = Ag+Cl_KSP称为溶度积常数，简称溶度积。它反应了物质的溶解能力 。沉淀溶 解Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011
4、Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.在一定温度下，难溶强电解质溶度积常数通式：AmBn mAn+ + nBm-Ksp = An+mBm-nm、n分别代表电离方程式中A、B离子的化学计量数。溶度积常数的意义：一定温度下，难溶强电解质饱和溶液中离子浓度的系数次方之积为一常数。KSP是温度的函数。但是通常温度对它影 响不大，所以在实际工作中，当温度变化 不大时，可采用常温下的数据。Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client
5、 Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.例如：PbCl2(s) Pb2+ + 2Cl- ;Ksp=Pb2+Cl-2Fe(OH)3 Fe3+ + 3OH- ; Ksp=Fe3+OH-3Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Clien
6、t Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.3)溶度积与溶解度的相互换算溶度积与溶解度都可表示物质的溶解能力，所 以它们之间必有联系。根据溶度积关系式，一般可以把溶解度和溶度 积进行互相换算。换算时注意的问题：浓度的单位必须采用mol/L.由于难溶电解质的溶解度都很小，即 溶液很稀，所以换算时，可以近似地 认为它们饱和溶液的密度和纯水一样
7、 为1g/cm3.Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.例题1 已知室温下氢氧化镁的溶解度为 6.53 10-3g/L。试求该温度下氢氧化镁的溶 度积。 例题2 已知BaSO4在
8、室温时的溶度积为1.1 10-10,求BaSO4的溶解度。Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.例题3 已知AgCl、Ag2CrO4的溶度积，求AgCl、Ag2CrO4的溶解度。
9、AgCl(s) Ag+ + Cl-S S Ksp = Ag+Cl- = S2 = 1.8*10-10SAgCl = Ksp = 1.8*10-10 = 1.3*10-5mol.l-1Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004
10、-2011 Aspose Pty Ltd.上式为AB型（1：1）溶解度计算式，同理可导出AB2和A2B型：SAg2CrO4= =6.5*10-5mol.l-1相同类型的电解质，可以通过溶度积数据直接比较溶解度大小，不同类型，不可直接比较。只有在难溶电解质基本不水解、且其组 分离子在水溶液中又是完全以离子的形 式存在的时候，才有上面简单的数学关 系。Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides fo
11、r .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.必须指出：溶度积与溶解度的换算式不适用于易水解的难溶电解质（如：ZnS、PbS）S2-+H2O HS-+OH- (不计二级水解) 结果：S2-浓度大大低于溶解度Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose
12、.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.不适用易形成离子对的难溶电解质。难溶弱电解质MX在水中存在下列平衡MX(s) MX(aq) Mm+ + Xn-(未离解分子）（如CaSO4饱和溶液有40%以上是以离子Ca2+.SO42-存在)Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5
13、.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.解题的一般步骤1） 写出化学方程式； 2） 用溶解度 S 表示出平衡浓度； 3） 写出 Ksp 的表达式； 4） 将已知数据代入后，求值或解方程Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile
14、 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.2、 溶度积原理对于沉淀-溶液平衡：AmBn mAn+ + nBm-非平衡态时：J = Cm(An+ )Cn(B m-)平衡态时：Ksp = An+ mB m-nEvaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Cli
15、ent Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.J = Ksp是饱和溶液，无沉淀析出，达到动态平衡；J Ksp 是过饱和溶液，反应向生成沉淀方向（逆向）进行，直至饱和为止。以上关系称为溶度积规则，J 称为离子积，利用此规则判断沉淀的生成和溶解。Evaluation only.Evaluation only. Created with As
16、pose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.二、难溶电解质沉淀的生成与溶解1、沉淀的生成沉淀生成的必要条件：根据溶度积规则，在难溶电解质溶液中是Qi KspEvaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.
