液体表面张力的测定Determination of surface tension of liquids.docx
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液体表面张力的测定Determination of surface tension of liquids.docx
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液体表面张力的测定Determinationofsurfacetensionofliquids
液体表面张力的测定(Determinationofsurfacetensionofliquids)
Experimentfive
Experimentfiveexperimentfive
Experimentfive
Determinationofsurfacetensionofliquids
Determinationofsurfacetensionofliquids-Determinationofsurfacetensionofliquids
Determinationofsurfacetensionofliquids
Twobillioneightmilliontwohundredandonethousandtwohundredandfive
2008201205,2008201205
2008201205Liusenior
LiuZizhengLiuZizheng
Liuzizheng
1objective
(1)todeterminethesurfacetensionofethanolsolutionwithdifferentconcentration,andcalculatethesurfaceadsorptioncapacityandthetransverseofethanolmolecule
Sectionalarea.
(2)tounderstandthepropertiesofsurfacetensionandtherelationshipbetweensurfacetensionandadsorptioncapacity.
(3)grasptheprincipleofmaximumbubblepressuremethodformeasuringsurfacetensionandsurfaceadsorptioncapacityofsolution.2theprincipleofexperimentisthatinaliquidinterior,theattractionofanymoleculeisbalanced.Butonthesurfaceoftheliquid
Themoleculesaredifferent.Becausethemoleculesonthesurfacelayerareattractedbythemoleculesintheliquidlayerontheonehand,theyareexposedtotheother
Theattractionofgasmoleculesoutsidetheliquid,andtheactionoftheformerisgreaterthanthatofthelatter.Therefore,onthesurfacelayerofliquidsurface
Eachmoleculeissubjectedtoanunbalancedforcethatisperpendiculartoanddirectedtowardtheinterioroftheliquid.Thisappealisapparentonthesurface
Themoleculespushinwardtomakeupthesmallestareaoftheliquid.Toincreasethesurfaceareaofaliquid,itisnecessarytohaveresistance
Todowork,increasethepotentialenergyofmolecules.Therefore,moleculesarelargerinthesurfacelayerthanintheliquid
Potentialenergy,whichissurfacefreeenergy,usuallyincreasesthemaximumworkrequiredbythesurfaceofasquaremeterbyAorincreases
Gchangeofsurfacefreeenergybyasquaremeters,knownasthesurfaceunitsurfaceenergy,anditsunitisJ-m-1;
Theforceactingonthesurfaceofaliquidandtheunitinitslengththatisusedtoshrinkitiscalledsurfacetension
Force,whoseunitisN.M-1.Thesurfaceenergyofaunitsurfaceofaliquidisequaltoitssurfacetension.
IfthesurfaceareaoftheliquidisincreasedbyS,thereversibleworkAshallbe:
-A=G=gammaS
(1)
Thesurfacetensionofliquidisrelatedtotemperature.Thehigherthetemperatureis,thesmallerthesurfacetensionis.Atthecriticaltemperature,
Liquidsandgasesaredivided,andsurfacetensionapproacheszero.Thesurfacetensionofaliquidisalsorelatedtothepurityoftheliquid
Inapureliquid(solvent),iftheimpurity(solute)isadded,thesurfacetensionchanges
Smalldependsonthenatureofthesoluteandtheamountadded.
Forpuresolvents,thesurfacelayeristhesameastheinternal,butnotthesolution.When
Whenthesoluteisadded,thesurfacetensionofthesolventchanges.Accordingtotheprincipleofminimumenergy,ifthesolutecandissolve
Thesurfacetensionoftheagentisthatthesoluteconcentrationinthesurfacelayershouldbegreaterthantheconcentrationinthesolution,iftheaddedsolutecan
Ifthesurfacetensionofthesolventisraised,thentheconcentrationofthesoluteinthesurfacelayershouldbelowerthantheconcentrationinsidethesolution.this
Thephenomenonthatthesurfaceconcentrationisdifferentfromtheconcentrationofthesolutioniscalledsurfaceadsorptionofthesolution.Atacertaintemperatureandpressure
Force,
Thesurfacetensionofsolutionandtheamountofadsorbedsolutesolutionandaddingthesolutionquality(i.e.concentration)
TherelationshipbetweenthembyGibbs(Gibbs)said:
Type:
fortheadsorptionofmol.m(gamma
TheconcentrationofR(mol.L-1);
Isthegasconstant
Thechangeofsurfacetensiontemperaturechangewithsolutionconcentrationrate(
Gamma?
/?
C)T<0,>0,gammasurfacelayer,theconcentrationisgreaterthantheconcentrationoftheinternalsolution
Effect。
Ifgammawithincreasingconcentrationofthe
Thedegreeofconcentrationislessthanthesolutionitself,
TheadsorptionofsolutesandconcentrationofC
C/gammamap,astraightline,
IfthemolecularNrepresents1m2surfacesolutenumber
WhereLisAvogadroconstant
From
(2)canbeseen,aslongastheconcentrationanddeterminationofsurfacetensionofsolution
Theadsorptionamountofgammasolution.
Inthisexperiment,themeasurementoftheconcentrationofsolutionisthecorrespondencebetweentheapplicationconcentrationandrefractiveindex
Isanapplicationofthemaximumbubblepressure
Tutu
chart
One
1.1.
1..
Beaker
Beaker;
;;
2.;
2.2.
Figure2.2-1
Isaschematicdiagramofapparatusformeasuringsurfacetensionofthemaximumbubblepressuremethod
Installedinthebranchtube5,thecapillary
Gamma=-((T)
(mol.m-1);gammasurfacetension(J,m-1);T
Absolutetemperature
Isthegasconstant(8.314J.K-1-mol-1).(
Gamma?
/?
Cchangeofsurfacetensiontemperaturechangewithsolutionconcentrationrate.Ifgammadecreaseswiththeincreaseoftheconcentrationof
Theconcentrationofsurfacelayerisgreaterthantheconcentrationoftheinternalsolution
Withtheincreasingconcentration(i.e.
Gamma?
/?
C)T>0,<0,gammasurfacelayer,thesolutionconcentration
Thatiscallednegativeadsorption.
TherelationshipbetweenCwithLangumuirisothermaladsorptionequation
C
Gamma
The
C
Gamma-
One
Gamma-K
Thus,theslopeofthelineandtheinterceptcanbeobtainedbyconstantKandgamma
Thenumberofsolutemoleculesonthesurface,then:
N=gamma-L
Thiscanbeaconstant,eachmoleculeinthecross-sectionalareaoccupiedbythesurface
Gamma-Am=1/
Aslongasthedeterminationofthesolutionconcentrationandthesurfacetensioncanbeobtainedunderdifferentconcentrations
Themeasurementoftheconcentrationofsolutionisthecorrespondencebetweentheapplicationconcentrationandrefractiveindex,
Isthemaximumbubblepressuremethod.
chart
Tutu
Figure2
Twenty-two
2-
-
-1
Eleven
One
Maximum
Thebiggest
Maximum
Determinationofsurfacetensionofbubblemethodapparatus
Determinationofsurfacetensiondeviceofbubblemethoddeterminationofsurfacetensionofbubblemethodequipment
Determinationofsurfacetensionofbubblemethodapparatus
Two
2.2.
2.dropfunnel
Thedroppingfunneldropfunnel
Dropfunnel;
;;
3.;
3.3.
Differentialpressuremeasuringinstrument3.digitalmicro
Digitalmicrodifferentialpressuremeasuringinstrumentdigitalmicrodifferentialpressuremeasuringinstrument
Differentialpressuremeasuringinstrumentdigitalmicro;
;;
4.;
4.4.
4.thermostat
Thermostatthermostat
Thermostaticdevice;
;;
;
Five
5.5.
5.withabranchtube
Withabranchtubewithbranchtube
Testtubewithbranchpipe;
;;
6.;
6.6.
6.capillary
Capillarycapillary
capillary
Isthemaximumbubblepressuremethodofmeasuringsurfacetensiondevicediagram
.Aliquidthatwilltestsurfacetension
Theendsurfaceofthecapillary6istangenttotheliquidsurfaceandtheliquidsurfacerisesalongthecapillarytube
(2)
Forabsolutetemperature(K)andCforC),Tmeans
Decreasewiththeincreaseofconcentration
Atthispoint,theconcentrationofthesolutionsurfacelayerisgreaterthantheconcentrationinsidethesolution,whichiscalledpositiveadsorption
Theconcentrationofthesolutionsurfacelayeratthistime
Isothermaladsorptionequationrepresentation:
Gammainfinity.
Thus,thesectionalareaoccupiedbyeachmoleculeonthesurfaceisAm:
Itcanbeobtainedatvariousconcentrations
Measurementofsurfacetension
Aliquidthatwilltestsurfacetension
Theliquidsurfacerisesalongthecapillaryandopensthedropfunnel.2ofthepistonslowlydrawsair,becausethepressureontheliquidlevelinthecapillary(Patmosphere)atthistime
Itislargerthanthepressureonthesurfaceofthetubeinthetesttube(Psystem),sotheliquidlevelinthecapillarygraduallydrops,andthebubbleslowlyescapesfromthecapillarytubeend.Duringtheformationofbubbles,theconcavesurfaceisproducedbecauseofthesurfacetension
AnadditionalpressurePispointedouttotheoutsideoftheliquidlevel,sothereisthefollowingrelationship:
Patmosphere=Psystem+deltaP
P=P,theatmosphericPsystem(3)additionalpressurePisproportionaltothesurfacetensionofthesolution,andisinverselyproportionaltotheradiusofcurvatureofthebubbleR
Tietype
P=2,gamma/R(4)
Ifthediameterofthecapillaryissmall,thebubblesformedcanbeconsideredspherical.Whenbubblesareformedjustbecauseofthesurface
Almostflat,sotheradiusofcurvatureisverylarge.Whenthebubbleishemispherical,theradiusofcurvatureisequaltocapillary
Thetubediameterisr,andtheRvalueisminimumatthistime.Asthebubbleincreasesfurther,itincreasesonly(seeFigure2),
Untiltheliquidlevelescapes.Accordingto(4),whenR=R,theadditionalpressureisthemaximum
P=2,gamma/r(5)
Thismaximumadditionalpressurecanbereadonthedigitalmicropressuredifferentialmeter.
chart
Tutu
Figure2
Twenty-two
2-
-
-2
Twenty-two
Fig.2Schematicofbubbleformation
Schematicdiagramofbubbleformation
Schematicdiagramofbubbleformation
Intheexperiment,theRisaconstantifthesamecapillaryandmanometerareused.Ifknown
Surfacetensionofliquidasastandard,aftertheexperimentmeasureditsdeltaP,youcanfindR.Thenjustusethisone
Thepvalueofotherliquidscanbemeasuredbytheinstrument.Thesurfacetensionofvariousliquidsca
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