电导法测定弱电解质电离常数及难溶盐溶解度.ppt

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1、电导法测定弱电解质电离常数及难溶盐溶解度DeterminationofWeakElectrolyte Ionization ConstantandsolubilityofHardlyDissolvedSaltbyConductivityMethodsContentPurposesandDemandsPrincipleApparatusandReagentprocedureDataRecordsandProcessingQuestionsAttentionsDemonstratedPurposesandDemands1.Todeterminethe

2、ionizationconstantofaceticacid.2.Todeterminethesolubilityofcalciumsulphate.3.Mastertheoperationofconductivitydetector.Principle1）Determinationofweakelectrolyteionizationconstant.Atcertaintemperature,theequilibriumofaceticacidionizationinwatercanbewrittenasfollowHAc=H++Ac－Init

3、ialc00egc(1-α)cαcαSo,ionizationconstantcouldbeexpressedas:Ionizationdegreeαinformula①isrelatedwithmolarconductivity.Thatis:Λ——molarconductivitywhenconcentrationiscΛ0——ultimatemolarconductivityifsolutionisdilutedillimitablyΛ0=L++L–（thesumofpositiveandnegativeionmolarconductivi

4、ty)canbelookuponliteratures.K——conductivity(s/cmorms/cmorμs/cm).Itcanbedeterminedthroughexperiment.C——concentration(mol•L-1orN•L－1)Addingequation.②into.①,weobtainthat④DrawagraphofcΛmagainst1/Λandgetabeelineofwhichslopeis:slope=Λ02×KcLookforΛ0onliteratures,andaccountoutKc.实验

5、原理2）Determinationofhardlydissolvedsalt’ssolubilityKc=Ksolution–KH2OKsolution——conductivityofsolutionKH2O——conductivityofwaterApparatusandReagentConductivitydetector1Superthermostatictrough1Conicalflask（250ml）2Conicalflask（50ml）3Pipette(20ml)2Beaker(100ml)10.1000MHAcsolutionCa

6、SO4(A.R)Procedure1）Determinationofweakelectrolyteionizationconstant1.Regulatethetemperatureofthermostatictroughat25℃±0.1℃.Puttwoconicalflasksoneofwhichisfilledwith120-130mlconductivewaterandanotherwith40mlHAc(0.1M)intothermostatictrough,andmaintainthetemperatureatthislevelfor

7、20min.2.Cleanaplatinumblackelectrodewithdistilledwaterandblotteditupbytheuseoffilterpaper(don’ttouchplatinum-black).Puttheelectrodeintotheconicalflaskfilledwith40mlHAcanddetecttheconductivity.RemovelofHAcsolutionandcomplementwith20mlconductivewaterthathasbeenkepttemperatureco

8、nstant,shakingup.Aftertemperatureiskeptconstantfor5min,determinethec