Lesson 3 Analytical Chemistry翻译

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1、Lesson3AnalyticalChemistryAnalyticalchemistryisthescienceofmakingquantitativemeasurements.Inpractice,quantifyinganalytesinacomplexsamplebecomesanexerciseinproblemsolving.Tobeeffectiveandefficient,analyzingsamplesrequiresexpertisein:1thechemistrythatcanoc

2、curinasample2analysisandsamplehandlingmethodsforawidevarietyofproblems(thetools-of-the-trade)3properdataanalysisandrecordkeepingTomeettheseneeds,AnalyticalChemistrycoursesusuallyemphasizeequilibrium,spectroscopicandelectrochemicalanalysis,separations,and

3、statistics.Analyticalchemistryrequiresabroadbackgroundknowledgeofchemicalandphysicalconcepts.Withafundamentalunderstandingofanalyticalmethods,ascientistfacedwithadifficultanalyticalproblemcanapplythemostappropriatetechnique(s).Afundamentalunderstandingal

4、somakesiteasiertoidentifywhenaparticularproblemcannotbesolvedbytraditionalmethods,andgivesananalysttheknowledgethatisneededtodevelopcreativeapproachesornewanalyticalmethods.1GravimetryGravimetryisthequantitativemeasurementofananalytebyweighingapure,solid

5、formoftheanalyte.Obtainingpuresolidsfromsolutionscontaininganunknownamountofametalionisdonebyprecipitation.Sincegravimetricanalysisisanabsolutemeasurement,itisaprincipalmethodforanalyzingandpreparingprimarystandards.Atypicalexperimentalproceduretodetermi

6、neanunknownconcentrationofananalyteinsolutionisasfollows:·quantitativelyprecipitatetheanalytefromsolution·collecttheprecipitatebyfilteringandwashittoremoveimpurities·drythesolidinanoventoremovesolvent·weighthesolidonananalyticalbalance·calculatetheanalyt

7、econcentrationintheoriginalsolutionbasedontheweightoftheprecipitateGravimetricDeterminationofIron:·Determineconstantweightofthecrucibles·Oxidationofironsample·Precipitationofironhydroxide·Ignitionofironhydroxidetoironoxide8·Determineconstantweightofthecr

8、uciblesplusironoxide·Calculationofironinthesample2TitrationTitrationisthequantitativemeasurementofananalyteinsolutionbycompletelyreactingitwithareagentsolution.Thereagentiscalledthetitrantandmusteitherbepreparedfromaprimar