高中化学沉淀溶解平衡课件很全新人教选修 36页

第10章沉淀平衡Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n10-1溶度积原理10-2沉淀与溶解习题Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n§10-1溶度积原理一般可用溶解度的大小来衡量物质在水中溶解能力的大小.物质溶解度(g/100g水)易溶物>0.1微溶物0.01~0.1难溶物<0.01Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n对难溶物来说,在它的饱和溶液中存在多相离子平衡.Ba2+SO42-一定T时:溶解溶解BaSO4(s)BaSO4(aq)Ba2+(aq)+SO42-(aq)沉淀沉淀一、溶度积常数Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\nBaSO4(s)BaSO4(aq)全部电离Ba2+(aq)+SO42-(aq)Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n平衡时Ksp=[Ba2+][SO42-]Ksp称为溶度积常数,简称溶度积(solubilityproduct).表示一定温度下，难溶电解质的饱和溶液中,各离子平衡浓度幂的乘积为一常数。Ba2++SO42-BaSO4(s)Ba2+(aq)+SO42-(aq)简写为BaSO4(s)设AmBn(s)mAn++nBm-Ksp=[An+]m[Bm-]nEvaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n化学式Ksp化学式KspAgCl1.56×10-10Cu2S2×10-47AgBr7.7×10-13CuCl1.02×10-6AgI1.5×10-16Fe(OH)21.64×10-14Ag2CrO49.0×10-12Fe(OH)31.1×10-36BaCO38.1×10-9HgS4×10-53BaSO41.08×10-10Li2CO31.7×10-3CaCO38.7×10-9MgCO32.6×10-5CaF23.95×10-11Mg(OH)21.2×10-11CaSO41.96×10-4PbSO41.06×10-8CuS8.5×10-45ZnS1.2×10-23溶度积常数(见p419附表6)Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\nKsp越大则难溶电解质在溶液中溶解趋势越大，反之越小。二、溶度积与溶解度的相互换算溶解度s的单位g/L或mol/L,即饱和时的浓度。AmBn(s)mAn++nBm-smsnsKsp=[An+]m[Bm-]n=[ms]m[ns]n=mmnnsm+nEvaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n例1:室温下,AgCl的溶解度是1.93×10-3g/L,求AgCl的溶度积。已知AgCl的摩尔质量为143.3g/mol。解：①把AgCl溶解度单位(g/L)换算成mol·L-1s=1.93×10-3g/L÷143.3g/mol=1.35×10-5mol·L-1②求KspAgCl(s)Ag++Cl-饱和、平衡1.35×10-51.35×10-5Ksp(AgCl)=[Ag+][Cl-]=(1.35×10-5)2=1.82×10-10答：AgCl的Ksp为1.82×10-10Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n例2:Mg(OH)2的Ksp=1.20×10-11在298K时,Mg(OH)2的溶解度为多少?解：Mg(OH)2(s)Mg2++2OH-设溶解度为s平衡时s2sKsp=[Mg2+][OH-]2=s(2s)2=4s3=1.2×10-11∴s=1.44×10-4mol·L-1答:氢氧化镁在298K时的溶解度为1.44×10-4mol·L-1。Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n例3:Ag2CrO4在298K时溶解度s=1.34×10-4mol·L-1求：Ksp解：Ag2CrO4(s)2Ag++CrO42-平衡时2×1.34×10-41.34×10-4Ksp=[Ag+]2[CrO42-]=(2×1.34×10-4)2×1.34×10-4=9.62×10-12答：铬酸银在298K时的Ksp=9.62×10-12由以上三个例题的结果可得到如下结论：①同种类型的难溶电解质，在一定温度下，Ksp越大则溶解度越大。②不同类型则不能用Ksp的大小来比较溶解度的大小，必须经过换算才能得出结论。Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n三、溶度积原理根据溶度积常数可以判断沉淀、溶解反应进行的方向。某难溶电解质溶液中，其离子浓度系数次方之积称离子积。用J表示。如：Ag2CrO4任意情况下的离子积为：J=c2(Ag+)×c(CrO42-)①当J=Ksp是饱和溶液无沉淀析出即平衡状态；②当JKsp是过饱和溶液,向生成沉淀的方向移动。Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n例在20mL0.0020mol·L-1Na2SO4溶液中加入20mL0.020mol·L-1BaCl2溶液，有无BaSO4沉淀生成？并判断SO42-离子是否沉淀完全？已知BaSO4的Ksp=1.07×10-10.解:（1）∴有BaSO4沉淀生成Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n即1.07×10-10≈0.0090x∴x=[SO42-]≈1.2×10-8mol·L-1⑵设平衡时[SO42-]=xmol·L-1沉淀完全是指离子残留量≤10-5mol·L-1故加入BaCl2可使SO42-沉淀完全Ksp=[Ba2+][SO42-]=(0.0090+x)x起始浓度/mol·L-10.0100.0010平衡浓度/mol·L-10.010﹣（0.0010-x）xBaSO4(s)Ba2++SO42-∴0.0090+x≈0.0090∵x很小Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n四、同离子效应和盐效应⒈同离子效应PbI2饱和溶液+KI(aq)→黄↓在难溶电解质溶液中加入含有共同离子的易溶强电解质，使难溶电解质溶解度降低的现象。2.盐效应在难溶电解质饱和溶液中加入不含相同离子的强电解质，将使难溶电解质的溶解度略为增大的现象。Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n例:298K时硫酸钡的溶解度为1.04×10-5mol·L-1，如果在0.010mol·L-1的硫酸钠溶液中的溶解度是多少？解：①先求KspBaSO4Ba2++SO42-1.04×10-51.04×10-5Ksp=[Ba2+][SO42-]=1.04×10-5×1.04×10-5=1.08×10-10Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n②求sNa2SO4→2Na++SO42-BaSO4Ba2++SO42-初00.01平衡ss+0.01≈0.01Ksp=[Ba2+][SO42-]=s×0.01s=Ksp/0.01=1.08×10-10/0.01=1.08×10-8mol·L-1s<<0.01,即前面的近似是合理的。答：溶解度是1.08×10-8mol·L-1。可见在溶液中离子的浓度不可能为零，我们通常当溶液中被沉淀离子浓度小于10-5mol·L-1时即可认为沉淀完全了。Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n§10-2沉淀与溶解一、沉淀的生成欲使某物质析出沉淀，必须使其离子积大于溶度积，即增大离子浓度可反应向着生成沉淀的方向转化。例：将等体积的4×10-3mol·L-1的AgNO3和4×10-3mol·L-1的K2CrO4溶液混合是否能析出Ag2CrO4沉淀?Ksp(Ag2CrO4)=1.0×10-12解：混合后因Ag2CrO42Ag++CrO42-c(Ag+)=2×10-3mol·L-1，c(CrO42-)=2×10-3mol·L-1J=c2(Ag+)×c(CrO42-)=(2×10-3)2×2×10-3=8×10-9J>Ksp∴有沉淀析出。答：能析出Ag2CrO4沉淀。Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n例:向1.0×10-3molL-1的K2CrO4溶液中滴加AgNO3溶液,求开始有Ag2CrO4沉淀生成时的[Ag+]?CrO42-沉淀完全时,[Ag+]=?假设反应前后体积不变。已知Ksp(Ag2CrO4)=1.0×10-12解:Ag2CrO42Ag++CrO42-Ksp=[Ag+]2[CrO42-]CrO42-沉淀完全时的浓度为1.0×10-5molL-1，故有Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n例：向0.1molL-1的ZnCl2溶液中通H2S气体至饱和时，溶液中刚有ZnS沉淀生成，求此时溶液的[H+]=?已知Ksp(ZnS)=2.0×10-22，H2S的Ka1=1.3×10-7，Ka2=7.1×10-15解:ZnSZn2++S2-Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\nH2S2H++S2-=0.21molL-1Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.Evaluationonly.CreatedwithAspose.Slidesfor.NET3.5ClientProfile5.2.0.0.Copyright2004-2011AsposePtyLtd.\n二、沉淀的溶解J