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Transcript
IBPrescribedPracticals,ExperimentalProcedures,andLabTechniques 1. Obtainingandusingexperimentaldataforderivingempiricalformulasfromreactions involvingmasschanges. § Determiningwaterofhydration/molarmassofhydrates § Molarmassofoxides § Combustionofmagnesium/copper Skillsandtechniques: Equipmentinvolved: § Usingatriple-beambalance § Triple-beambalance § Weighingbydifference § Crucibleandlid § Stoichiometriccalculationsinvolvingmolar § Crucibletongs mass,%composition,moleratio,empirical § watchglass andmolecularformula § Bunsenburner § Uncertaintypropagation 2. Useoftheexperimentalmethodoftitrationtocalculatetheconcentrationofasolution byreferencetoastandardsolution. § Standardizinganacidorabase § Determiningthestrengthofanacidorabase § Determiningexactconcentrationsofgivenreagents. Skillsandtechniques: § Makingvolumetricsolutions § Makingastandardsolution § Readingvolumeswithaccuracyand precision § Conductingatitrationwithanend-point asclosetotheequivalencepointas possible § Uncertaintypropagation • • • • Equipmentinvolved: § Burettes § Volumetricpipettesandbulbs § Volumetricflasks § Erlenmeyerflasks § Retortstand § Buretteclamps § Graduatedcylinder PotassiumHydrogenPhthalate(KHP)isanacidicsaltoftenusedastheprimarystandard forthestandardizationofabaselikeNaOH. AprimarystandardlikeKHPispure,stable,andhasnowatersofhydration.Italsohasa relativelyhighmolarmassthatallowsforahighaccuracy. AsolutionofKHPisusedtodeterminetheexactconcentrationofasolutionlikeNaOH. NaOHcannotbeusedtomakeastandardsolutionbecauseitishygroscopicand unstable,therefore,itcannotbemadetoanexactconcentration. Sodiumcarbonate,Na2CO3,isoftenusedtostandardizeacids. 3. Obtainingandusingexperimentalvaluestocalculatethemolarmassofagasfromthe idealgasequation. § Usingtheidealgaslaw,PV=nRT,tocalculatethenumberofmolesofagas/volatile substance § Usingitsmasstodeterminethemolarmass. Skillsandtechniques: § Usingtheidealgasequation § Usingagassyringe § Usingagascollectiontube § Usingapressuresensor Equipmentinvolved: § Gassyringe § Gascollectiontube § Pressuresensor § Thermometer § Oven § Weighingscale 4. Acalorimetryexperimentforanenthalpyofreactionshouldbecoveredandtheresults evaluated. § Determineenergychangesinreactions:neutralization,combustion,formation, decomposition,etc. § UsingHess’sLawtodetermineenthalpychangeforotherwiseunfeasiblereactions Skillsandtechniques: Equipmentinvolved: § Buildingacalorimeter § Calorimeter § UsingHess’sLaw § Timer/stopwatch § Obtainingaheatingand/orcoolingcurve § Thermometer/temperatureprobe § Extrapolatingthecoolingcurveto § Datacollectionsoftware minimizeheatlosstothesurroundings http://ibchem.com/IB16/04.17.htm § Evaluatingrandomandsystematicerrors 5. Investigationofratesofreactionsindependentlyandevaluationofresults. § Theiodineclockreaction § Decompositionofhydrogenperoxide § ReactionbetweenHClandMg/Zn Skillsandtechniques: Equipmentinvolved: § Measuringchangeinaquantitypertime § Timer/stopwatch § Usingpressuresensors/colorimeter/ § Sensors/probes eudiometer/temperatureprobes/pH § Datacollectionsofware probes,etc. § Drawing/interpreting/analyzingquantity vs.rate/timegraphs • • Thesereactionshavetoberelativelyslow,tobeabletomeasure/observethem. Theycanbecontinuouslymonitoredorcanmeasureaspecificquantityatagiventime interval. 6. Acid-basetitrationswithdifferentindicators. § Similarto#2 § KnowthepHrangesofdifferentindicatorsandtheirrespectivechangesincolour,asin yourDataBooklet. E.g.formethylorange,thepHrangeis3.1–4.4andthecolourchangesfromredto yellow.ThismeansthatasolutionwithpH≤3.1willberedandpH≥4.4willbe yellow.However,ifthepHofthesolutionisbetween3.1and4.4,thesolutionwill appearorange.Thisisknownasitstransitioncolour. Forindicatorslikephenolphthalein,thatgoesfromcolourlesstopink,thereisno transitioncolour–thepHchangeisimmediatelyobserved. 7. BefamiliarwiththeuseofapHmeteranduniversalindicator. § Similarto#2and#6. § TheuseofapHprobeanddatacollectionsoftwareproducesatitrationcurve. § Universalindicatorisamixtureofafewdifferentindicatorsinalcoholsolution,to allowfordifferentcolourchangesacrossawiderpHrange. 8. Performanceoflaboratoryexperimentsinvolvingatypicalvoltaiccellusingtwometal/ metalionhalf-cells. § Conductingredoxreactionstoconvertchemicalenergytoelectricalenergy. § Variablesinclude:changingT,[metalion],saltbridgelengthand[salt],etc. § Variationscouldincludeattachingasmalllightbulbtothecircuitandusingthe electricalenergyproducedtolightthebulb,insteadofavoltmeter. Skillsandtechniques: Equipmentinvolved: § Settingupanelectrochemicalcell § Metal § Correctlyidentifyingandusingthe § Metalsalt anode,cathode,andsaltbridge. § U-tubeforsaltbridgeoraporouscup § Determinationofaspontaneousreaction § Electrolyteforsaltbridge withthestrongestoxidizingandreducing § Voltmeter/multimeter agentstoproducethehighestvoltage. § Alligatorclips 9. Constructionof3Dmodels(realorvirtual)oforganicmolecules. § Usingmodelkitstodepictbonding,structure,andhybridization. § Virtual:http://chemagic.org/molecules/mini.html http://molview.org 10. Performlabexperimentswhichcouldincludesinglereplacementreactionsinaqueous solutions. § Thesecanincludeexperimentsacrossdifferenttopicscoveredpreviously,e.g. determinewatersofhydration;kineticsandequilibriumexperimentse.g.iodineclock, magnesiumandHCl;redoxreactionsandtitrations,e.g.withiodineorthereactivity series.
