仪器分析英文原版教案(8)

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1、IntroductiontoElectrochemistry(Chapter22)Manydifferentelectroanalyticalmethods:¥fast¥inexpensive¥insitu¥informationaboutoxidationstatesstoichiometryrateschargetransferequilibriumconstantsCEM333page10.1ElectrochemicalCells:Oxidationandreduction(redox)

2、reactionsSeparatespeciestopreventdirectreaction(Fig22-1)Mostcontain¥externalwires(electronscarrycurrent)¥ionsolutions(ionscarrycurrent)¥interfacesorjunctionsAllcontain¥completeelectricalcircuit¥conductingelectrodes(metal,carbon)CEM333page10.2Electron

3、stransferredatelectrodesurfaceatliquid/solidinterfacePotentialdifference(voltage)ismeasureoftendencytomovetoequilibriumGalvaniccell-celldevelopsspontaneouspotentialdifference2+2+Overall:Zn(s)+Cu(aq)®Zn(aq)+Cu(s)2+-Zn(s)®Zn+2eOxidationHalfreactions:2+

4、-Cu+2e®Cu(s)ReductionConvention:ReductionatCathodeOxidationatAnodeGalvaniccell-Znanode(negative),Cucathode(positive)CEM333page10.3Electrolyticcells-requirepotentialdifferencegreaterthangalvanicpotentialdifference(todriveawayfromequilibrium)2+-Zn(s)®Z

5、n+2eOxidationGalvaniccell2+-Cu+2e®Cu(s)Reduction2+-Zn+2e®Zn(s)ReductionElectrolyticcell2+-Cu(s)®Cu+2eOxidationElectrolyticcell-Zncathode(positive),Cuanode(negative)ManychemicallyreversiblecellsShort-HandCellnotation:Convention:AnodeonLeftZn

6、ZnSO4(0.0

7、1M)

8、

9、CuSO4(0.01M)

10、Culiquid-liquidinterfaceGalvaniccellaswrittenElectrolyticcellifreversedCEM333page10.4Notallcellshaveliquid-liquidjunctions(Fig22-3)+-AgCl(s)®Ag(aq)+Cl(aq)H2(g)®H2(aq)+-Cathode:Ag(aq)+e®Ag(s)+-Anode:H2(aq)®2H(aq)+2e+-Overall:2AgCl(s)

11、+H2(g)®2Ag(s)+2H+2Cl+-Pt,H2(p=1atm)

12、H(0.01M),Cl(0.01M),AgCl(sat'd)

13、AgCEM333page10.5ElectrodePotentials:¥CellpotentialisdifferencebetweenanodeandcathodepotentialEcell=Ecathode-Eanodewhenhalf-reactionswrittenasreductionsExample:+-2AgCl(s)+H2(g)®2Ag(s)+

14、2H+2Cl--2AgCl(s)+2e«2Ag(s)+2Cl+-2H+2e«H2(g)electronsonleftGalvaniccellEcell=Ecathode-Eanode=+0.46VCan'tmeasurepotentialoneachelectrodeindependently-onlydifferencesCEM333page10.6Standardreferenceelectrodeisusuallystandardhydrogenelectrode(SHE)+Pt,H2(p