过氧化氢含量的测定

DeterminationofConcentrationbyOxidation-ReductionTitrationHydrogenPeroxide2013.10.25ContentExperimentalObjective···········································2ExperimentalPrinciple············································3ApparatusandReagents··········································5ExperimentalProcedures·········································7Notice········································································13QuestionsandDateAnalysis··································141ExperimentalObjectiveLearnthemethodsofhowtoprepare,calibrateandsaveKMnO4standardsolution.LearnthemethodsofhowtodetermineH2O2concentrationbytheKMnO4standardsolution.Practiceusingselfindicator.Acquirethesamplingmethodsofliquidsamples.2TheKMnO4reagentoftencontainingimpurities,itcannotbeusedtoprepareexactconcentrationsolution.Therefore,thetitrationisnecessaryforKMnO4solution.ExperimentalPrincipleInthisexperiment,potassiumpermanganatesolutionisstandardizedwiththehelpofstandardsodiumoxalatesolution.Thereactionthatoccurshereisoxidationandreductionreaction.3Hydrogenperoxide(H2O2)isrelativelyunstableanddecomposestoformwaterandoxygengas.ExperimentalPrincipleOnemethodofdeterminingtheconcentrationofahydrogenperoxide(H2O2)solutionisbytitrationwithasolutionofpotassiumpermanganate,KMnO4,ofknownconcentration.4ApparatusandReagentsApparatus:1.Electronicbalance(1/10000)2.Reagentbottle(brown)3.Acidburette4.Cylinder5.Measuringpipette6.Erlenmeyerflask7.Volumetricflask8.ElectrothermostaticwaterbathNameofthechemicalsused:1.Sodiumoxalatesolution(Na2C2O4,S)2.H2SO4solution(3mol/L)3.Potassiumpermanganatesolution(KMnO4,0.1mol/L)4.Hydrogenperoxide(H2O2,3%)5ApparatusandReagentsElectroThermostaticWaterBathElectronicBalance6ExperimentalProceduresTake25mLKMnO4solution(0.1mol/L)intoa500mLreagentbottleanddiluteitto250mLbydistilledwater.PreparingtheTitrant(KMnO4)RinseyourburetwithafewmillilitersoftheKMnO4solution:poursomein,rotatetheburetaroundtocoatallthesurfaces,andthenrinseyourstopcockbyopeningitandallowingtheKMnO4todrainintoawastebeaker(Don’tletitgodownthesink!).DoNOTrinseyourburetwithwater.FillyourburetwiththeKMnO4solution.(Makesureyourstopcockisclosedbeforeyoustarttopour!)Prepareyourlabnotebookandwearyourgoggles.YourKMnO4solutionisnowreadyfortitration.7Weighoutabout0.08gofNa2C2O4intoa250mLerlenmeyerflask.Dissolvethesampleinabout50mLofdistilledwaterandacidifywith15mLof3MH2SO4.Placetheflaskinaelectrothermostaticwaterbathandheattoatemperatureof70-80oC.PreparingtheAnalyte(Na2C2O4)ExperimentalProceduresYouranalyteisnowreadyfortitration.8TitratetheNa2C2O4solutionwiththeKMnO4,swirlingconstantly.BecarefulnottoaddtheKMnO4solutiontooquickly.TheendpointhasbeenreachedwhenonedropofKMnO4turnstheentiresolutionafaintpinkcolorthatdoesnotdisappearwhentheflaskisswirled.ExperimentalProceduresRecordyourobservations(watchcarefully)andthevolumeoftitrantused.Repeatthetitrationandcalculations.PerformingtheTitration9ExperimentalProceduresPreparingtheTitrant(KMnO4)TheprocessesofpreparingKMnO4solutionissimilarwiththeaboveexperiment.Youranalyteisnowreadyfortitration.PreparingtheAnalyte(3%H2O2)Usingameasuringpipette,transfer0.50mLoffreshH2O2toanErlenmeyerflask.Dilutetheperoxidewith20mLdistilledwaterandadd7mLof3MH2SO4.10ExperimentalProceduresPerformingtheTitrationPerformthistitration:slowdownwhenyoustarttoseealingeringcolorchange.Thisoneiseasytoovershoot,sogoslowtowardstheend:dropbydrop.Recordyourobservations(watchcarefully)andthevolumeoftitrantused.Repeatthetitrationandcalculations.112734651ExperimentalProcedures12NoticeThesulfuricacid,H2SO4,usedissignificantlyconcentrated.WeargogglesandglovewhenworkingwithitandimmediatelyneutralizeanyspillswithAcidLock.Ifyouspillanyacidonyourskin,immediatelyrinsewithwater.Althoughthepotassiumpermanganate,KMnO4,usedinthisexperimentisdilute,itisstillapotentoxidizerandstainsskinandclothing.Weargogglesandapronsandcleanupanyspillsimmediatelywithwetpapertowels.Warnings!13WhatisthestoichiometryofthereactionbetweenKMnO4and