版权说明：本文档由用户提供并上传，收益归属内容提供方，若内容存在侵权，请进行举报或认领
文档简介
QuantitativeAnalysis
定量分析
QuantitativeAnalysis
定量分析CHAPTER10
EFFECTOFELECTROLYTESONCHEMICALEQUILIBRIA
CHAPTER10
EFFECTOFELECTROLY
Thepositionofmostsolutionequilibriadependsontheelectrolyteconcentrationofthemedium,evenwhentheaddedelectrolytecontainsnoionincommonwiththoseinvolvedintheequilibrium. H3AsO4+3I-+2H+ H3AsO3+I3-+H2O Ifanelectrolyte,suchasbariumnitrate,potassiumsulfate,orsodiumperchlorate,isaddedtothissolution,thecolorofthetriiodideionbecomeslessintense.ThisdecreaseincolorintensityindicatesthattheconcentrationofI3-hasdecreasedandthattheequilibriumhasbeenshiftedtotheleftbytheaddedelectrolyte. Thepositionofmostsolutio定量分析10电解质对化学平衡的影响EFFECT-OF-ELECTROLYTES-ON-CHEMICAL-EQUILIBRIA课件
HowDoIonicChargesAffectEquilibria? Themagnitudeoftheelectrolyteeffectishighlydependentonthechargesoftheparticipantsinanequilibrium.Whenonlyneutralspeciesareinvolved,thepositionofequilibriumisessentiallyindependentofelectrolyteconcentration.Withionicparticipants,themagnitudeoftheelectrolyteeffectincreaseswithcharge.Ina0.02Msolutionofpotassiumnitrate,thesolubilityofbariumsulfateislargerthanitisinpurewaterbyafactorof2.Thesolubilityofbariumiodatebyafactorofonly1.25andthatofsilverchlorideby1.2 HowDoIonicChargesAffectE定量分析10电解质对化学平衡的影响EFFECT-OF-ELECTROLYTES-ON-CHEMICAL-EQUILIBRIA课件定量分析10电解质对化学平衡的影响EFFECT-OF-ELECTROLYTES-ON-CHEMICAL-EQUILIBRIA课件 WhatIstheEffectofIonicStrengthonEquilibria? Theeffectofaddedelectrolyteonequilibriaisindependentofthechemicalnatureoftheelectrolytebutdependsonapropertyofthesolutioncalledtheionicstrength.Thisquantityisdefinedas ionicstrength=
=1/2([A]ZA2+[B]ZB2+[C]ZC2+…) Where[A],[B],[C],…representthemolarspeciesconcentrationsofionsA,B,C,…andZA,ZB,ZC,…aretheirioniccharges. Forsolutionswithionicstrengthsof0.1Morless,theelectrolyteeffectisindependentofthekindofionsanddependentonlyontheionicstrength.Thisindependencewithrespecttoelectrolytespeciesdisappearsathighionicstrengths. WhatIstheEffectofIonicS TheSaltEffect Theelectrolyteeffectresultsfromtheelectrostaticattractiveandrepulsiveforcesthatexistbetweentheionsofanelectrolyteandtheionsinvolvedinanequilibrium.Theseforcescauseeachionfromthedissociatedreactanttobesurroundedbyasheathofsolutionthatcontainsaslightexcessofelectrolyteionsofoppositecharge.Whenabariumsulfateprecipitateisequilibratedwithasodiumchloridesolution,eachdissolvedbariumionissurroundedbyanionicatmospherecarriesasmallnetnegativecharge. TheSaltEffect…continued…
Eachsulfateionissurroundedbyanionicatmospherethattendstobeslightlypositive.Thesechargedlayersmakethebariumionssomewhatlesspositiveandthesulfateionssomewhatlessnegativethantheywouldbeintheabsenceofelectrolyte.Theconsequenceofthiseffectisadecreaseinoverallattractionbetweenbariumandsulfateionsandanincreaseinsolubility,whichbecomesgreaterasthenumberofelectrolyteionsinthesolutionbecomeslarger.…continued… ACTIVITYCOEFFICIENTS
Chemistsusethetermactivity,a,toaccountfortheeffectsofelectrolytesonchemicalequilibria.Theactivity,oreffectiveconcentration,ofspeciesXdependsontheionicstrengthofthemediumandisdefinedas aX=x[X] where,aXistheactivityofX,[X]isitsmolarconcentration,andxisadimensionlessquantitycalledtheactivitycoefficient. ACTIVITYCOEFFICIENTS…continued… TheactivitycoefficientandthustheactivityofXvarywithionicstrengthsuchthatsubstitutionofaXfor[X]inanyequilibrium-constantexpressionfreesthenumericalvalueoftheconstantfromdependenceontheionicstrength.IfXmYnisaprecipitate,thethermodynamicsolubilityproductexpressionisdefinedbytheequation Ksp=aXm.aYn Ksp=Xm.Yn.[X]m[Y]n=Xm.Yn.K`sp HereK`spistheconcentrationsolubilityproductconstantandKspisthethermodynamicequilibriumconstant.…continued… PropertiesofActivityCoefficients
1.Theactivitycoefficientofaspeciesisameasureoftheeffectivenesswithwhichthatspeciesinfluencesanequilibriuminwhichitisaparticipant.Inverydilutesolution,wheretheionicstrengthisminimal,thiseffectivenessbecomesconstantandtheactivitycoefficientbecomesunity.Undersuchcircumstances,theactivityandthemolarconcentrationareidentical(asarethermodynamicandconcentrationequilibriumconstants).Astheionicstrengthincreases,however,anionlosessomeofitseffectivenessanditsactivitycoefficientdecreases.Atmoderateionicstrengths,x<1;asthesolutionapproachesinfinitedilution,however,x1andthusax[X]andK`sp
Ksp PropertiesofActivityCoeffi定量分析10电解质对化学平衡的影响EFFECT-OF-ELECTROLYTES-ON-CHEMICAL-EQUILIBRIA课件…continued…
2.Insolutionsthatarenottooconcentrated,theactivitycoefficientforagivenspeciesisindependentofthenatureoftheelectrolyteanddependentonlyontheionicstrength. 3.Foragivenionicstrength,theactivitycoefficientofaniondepartsfartherfromunityasthechargecarriedbythespeciesincreases.Theactivitycoefficientofanunchargedmoleculeisapproximatelyunity,regardlessofionicstrength. 4.Atanygivenionicstrength,theactivitycoefficientsofionsofthesamechargeareapproximatelyequal.Thesmallvariationsthatdoexistcanbecorrelatedwiththeeffectivediameterofthehydratedions. 5.Theactivitycoefficientofagiveniondescribesitseffectivebehaviorinallequilibriainwhichitparticipates.…continued…
TheDebye-HuckelEquation
P.DebyeandE.Huckelderiveatheoreticalexpressionthatpermitsthecalculationofactivitycoefficientsofionfromtheirchargeandtheiraveragesize.Thisequationtakestheform
where,x=activitycoefficientofthespeciesX
Zx=chargeonthespeciesX =ionicstrengthofthesolution x=effectivediameterofthehydratedionXin nanometer(10-9m)
2 TheDebye-HuckelEquation2…continued…
Theconstants0.51and3.3areapplicabletoaqueoussolutionat25oC;Themagnitudeofxappearstobeapproximately0.3nmformostsinglychargedions;then,thedenominatoroftheDebye-Huckelequationsimplifiestoapproximately1+.Forionswithhighercharge,xmaybeaslargeas1.0nm.…continued… 定量分析10电解质对化学平衡的影响EFFECT-OF-ELECTROLYTES-ON-CHEMICAL-EQUILIBRIA课件 OmittingActivityCoefficientsin EquilibriumCalculations Weshallordinarilyneglectactivitycoefficientsandsimplyusemolarconcentrationsinapplicationoftheequilibriumlaw.Thisrecoursesimplifiesthecalculationsandgreatlydecreasestheamountofdataneeded.Formostpurposes,theerrorintroducedbytheassumptionofunityfortheactivitycoefficientisnotlargeenoughtoleadtofalseconclusions.Significantdiscrepanciesoccurwhentheionicstrengthislarge(0.01orlarger)orwhentheionsinvolvedhavemultiplecharges.Withdilutesolutions(ionicstrength<0.01)ornonelectrolytesorofsinglychargedion,theuseofconcentrationsinamass-lawcalculationoftenprovidedreasonablyaccurateresults. OmittingActivityCoefficient定量分析10电解质对化学平衡的影响EFFECT-OF-ELECTROLYTES-ON-CHEMICAL-EQUILIBRIA课件
QuantitativeAnalysis
定量分析
QuantitativeAnalysis
定量分析CHAPTER10
EFFECTOFELECTROLYTESONCHEMICALEQUILIBRIA
CHAPTER10
EFFECTOFELECTROLY
Thepositionofmostsolutionequilibriadependsontheelectrolyteconcentrationofthemedium,evenwhentheaddedelectrolytecontainsnoionincommonwiththoseinvolvedintheequilibrium. H3AsO4+3I-+2H+ H3AsO3+I3-+H2O Ifanelectrolyte,suchasbariumnitrate,potassiumsulfate,orsodiumperchlorate,isaddedtothissolution,thecolorofthetriiodideionbecomeslessintense.ThisdecreaseincolorintensityindicatesthattheconcentrationofI3-hasdecreasedandthattheequilibriumhasbeenshiftedtotheleftbytheaddedelectrolyte. Thepositionofmostsolutio定量分析10电解质对化学平衡的影响EFFECT-OF-ELECTROLYTES-ON-CHEMICAL-EQUILIBRIA课件
HowDoIonicChargesAffectEquilibria? Themagnitudeoftheelectrolyteeffectishighlydependentonthechargesoftheparticipantsinanequilibrium.Whenonlyneutralspeciesareinvolved,thepositionofequilibriumisessentiallyindependentofelectrolyteconcentration.Withionicparticipants,themagnitudeoftheelectrolyteeffectincreaseswithcharge.Ina0.02Msolutionofpotassiumnitrate,thesolubilityofbariumsulfateislargerthanitisinpurewaterbyafactorof2.Thesolubilityofbariumiodatebyafactorofonly1.25andthatofsilverchlorideby1.2 HowDoIonicChargesAffectE定量分析10电解质对化学平衡的影响EFFECT-OF-ELECTROLYTES-ON-CHEMICAL-EQUILIBRIA课件定量分析10电解质对化学平衡的影响EFFECT-OF-ELECTROLYTES-ON-CHEMICAL-EQUILIBRIA课件 WhatIstheEffectofIonicStrengthonEquilibria? Theeffectofaddedelectrolyteonequilibriaisindependentofthechemicalnatureoftheelectrolytebutdependsonapropertyofthesolutioncalledtheionicstrength.Thisquantityisdefinedas ionicstrength=
=1/2([A]ZA2+[B]ZB2+[C]ZC2+…) Where[A],[B],[C],…representthemolarspeciesconcentrationsofionsA,B,C,…andZA,ZB,ZC,…aretheirioniccharges. Forsolutionswithionicstrengthsof0.1Morless,theelectrolyteeffectisindependentofthekindofionsanddependentonlyontheionicstrength.Thisindependencewithrespecttoelectrolytespeciesdisappearsathighionicstrengths. WhatIstheEffectofIonicS TheSaltEffect Theelectrolyteeffectresultsfromtheelectrostaticattractiveandrepulsiveforcesthatexistbetweentheionsofanelectrolyteandtheionsinvolvedinanequilibrium.Theseforcescauseeachionfromthedissociatedreactanttobesurroundedbyasheathofsolutionthatcontainsaslightexcessofelectrolyteionsofoppositecharge.Whenabariumsulfateprecipitateisequilibratedwithasodiumchloridesolution,eachdissolvedbariumionissurroundedbyanionicatmospherecarriesasmallnetnegativecharge. TheSaltEffect…continued…
Eachsulfateionissurroundedbyanionicatmospherethattendstobeslightlypositive.Thesechargedlayersmakethebariumionssomewhatlesspositiveandthesulfateionssomewhatlessnegativethantheywouldbeintheabsenceofelectrolyte.Theconsequenceofthiseffectisadecreaseinoverallattractionbetweenbariumandsulfateionsandanincreaseinsolubility,whichbecomesgreaterasthenumberofelectrolyteionsinthesolutionbecomeslarger.…continued… ACTIVITYCOEFFICIENTS
Chemistsusethetermactivity,a,toaccountfortheeffectsofelectrolytesonchemicalequilibria.Theactivity,oreffectiveconcentration,ofspeciesXdependsontheionicstrengthofthemediumandisdefinedas aX=x[X] where,aXistheactivityofX,[X]isitsmolarconcentration,andxisadimensionlessquantitycalledtheactivitycoefficient. ACTIVITYCOEFFICIENTS…continued… TheactivitycoefficientandthustheactivityofXvarywithionicstrengthsuchthatsubstitutionofaXfor[X]inanyequilibrium-constantexpressionfreesthenumericalvalueoftheconstantfromdependenceontheionicstrength.IfXmYnisaprecipitate,thethermodynamicsolubilityproductexpressionisdefinedbytheequation Ksp=aXm.aYn Ksp=Xm.Yn.[X]m[Y]n=Xm.Yn.K`sp HereK`spistheconcentrationsolubilityproductconstantandKspisthethermodynamicequilibriumconstant.…continued… PropertiesofActivityCoefficients
1.Theactivitycoefficientofaspeciesisameasureoftheeffectivenesswithwhichthatspeciesinfluencesanequilibriuminwhichitisaparticipant.Inverydilutesolution,wheretheionicstrengthisminimal,thiseffectivenessbecomesconstantandtheactivitycoefficientbecomesunity.Undersuchcircumstances,theactivityandthemolarconcentrationareidentical(asarethermodynamicandconcentrationequilibriumconstants).Astheionicstrengthincreases,however,anionlosessomeofitseffectivenessanditsactivitycoefficientdecreases.Atmoderateionicstrengths,x<1;asthesolutionapproachesinfinitedilution,however,x1andthusax[X]andK`sp
Ksp PropertiesofActivityCoeffi定量分析10电解质对化学平衡的影响EFFECT-OF-ELECTROLYTES-ON-CHEMICAL-EQUILIBRIA课件…continued…
2.Insolutionsthatarenottooconcentrated,theactivitycoefficientforagivenspeciesisindependentofthenatureoftheelectrolyteanddependentonlyontheionicstrength. 3.Foragivenionicstrength,theactivitycoefficientofaniondepartsfartherfromunityasthechargecarriedbythespeciesincreases.Theactivitycoefficientofanunchargedmoleculeisapproximatelyunity,regardlessofionicstrength. 4.Atanygivenionicstrength,theactivitycoefficientsofionsofthesamechargeareapproximatelyequal.Thesmallvariationsthatdoexistcanbecorrelatedwiththeeffectivediameterofthehydratedions. 5.Theactivitycoefficientofagiveniondescribesitseffectivebehaviorinallequilibriainwhichitparticipates.…continued…
TheDebye-HuckelEquation
P.DebyeandE.Huckelderiveatheoreticalexpressionthatpermitsthecalculationofactivitycoefficientsofionfromtheirchargeand
温馨提示
- 1. 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 宠物医院宠物治疗费用明细表
- 智能硬件产品销售合同书
- 航空维修合作协议
- 高中生物科技发展故事征文
- 汉阳轻钢活动房施工方案
- 软件产品研发委托代理协议
- 卫辉脉冲喷淋塔施工方案
- 湛江英式花园施工方案
- 2024年保险职业学院单招职业技能测试题库带答案
- 农业用水合同
- 电力行业安全风险管理措施
- 川藏铁路勘察报告范文
- 新零售智慧零售门店解决方案
- 小学一年级数学20以内的口算题(可直接打印A4)
- 肿瘤放射治疗体位固定技术
- 上海黄浦区2025届物理高一第一学期期末质量跟踪监视模拟试题含解析
- 肺结核课件教学课件
- 新生儿心脏病护理查房
- 规划设计行业数字化转型趋势
- 2024年广告代理合同的广告投放范围与分成比例
- 物业年终总结汇报工作
评论
0/150
提交评论