化學專業(yè)英語馬永祥翻譯36課

1、36沸點和蒸餾沸點和蒸餾BoilingPointsofPureLiquids沸點的純液體Anygivenliquidwhenadmittedintoaclosedevacuatedspaceevapatesuntilthevapattainsacertaindefinitepressurewhichdependsonlyuponthetemperature.Thispressurewhichisthepressureexertedbyt

2、hevapinequilibriumwiththeliquidisthevappressureoftheliquidatthattemperature.Asthetemperatureincreases.thevappressureofatypicalliquidxincreasesregularlyasshownbythegeneralizedvappressuretemperaturecurveBCinFig.5.任何給定的液體當進

3、入一個封閉的疏散空間蒸發(fā)到蒸汽形成某種明確的壓力僅僅依賴于溫度。這種壓力這是由蒸汽壓力與液體平衡的是液體的蒸氣壓在溫度。隨著溫度的升高。這個壓力，是通過在與液體平衡的蒸汽施加的壓力，是液體在該溫度下的蒸汽壓，其隨著溫度的增加而增加。一個典型液體x的蒸汽壓的增加經(jīng)常如圖五所示，廣義蒸汽壓溫度曲線BC。AtthetemperatureTpwherethevappressurereaches101.3kPa.xbeginstoboilTpis

4、calledtheNMALBOILINGPOINTofx.Everyliquidwhichdoesnotdecomposebefeitsvappressurereaches101.3kPa.hasitsownacteristicboilingpoint.Ingeneraltheboilingpointofasubstancedependsuponthemassofitsmoleculesthestrengthoftheattractiv

5、efcesbetweenthem.Fagivenhomologousseriestheboilingpointsofthemembercompoundsrisefairlyregularlywithincreasingmolecularweight.在溫度、Tp那里的蒸汽壓力達到101.3kPa。開始煮和xTp被稱為正常沸點液體的x。在這個溫度，當蒸汽壓達到101.3kPa時，液體x開始沸騰，這個蒸汽壓力被叫做x的正常沸點。任何一種液體

6、在它的蒸汽壓達到101.3kPa之前都不分解，每種液體的沸點都有其自身的特點。一般來說一種物質的沸點取決于它的分子質量和它們之間的引力的強度。對于一個給定的同系物，其成員化合物的沸點隨分子量的增加而增加。Polarliquidstendtoboilhigherthannonpolarliquidsofthesamemolecularweightassociatedpolarliquidsusuallyboilconsiderablyhi

7、gherthannonassociatedpolarcompounds.極性液體的沸點往往高于相同分子量的非極性液體，而相關的極性液體的沸點遠遠高于一般的極性化合物。Theboilingpointisaacteristicconstantthatiswidelyusedintheidentificationofliquids.Becauseofitsmarkeddependenceuponpressureitsrathererratic

8、responsetoimpuritieshoweveritisgenerallylessreliableusefulinacterizationasacriterionofpuritythanisthemeltingpointfsolids1.沸點是一個常數(shù)廣泛用于識別液體。然而，由于對壓力的顯著依賴性和對雜質的相當無規(guī)律的反應，沸點用于鑒別和作為純度的判據(jù)方面，較之固體的熔點一般不太可信和較少使用。BoilingPointsofSol

9、utions沸點的解決方案Thenmalboilingpointofanysolutionisthetemperatureatwhichthetotalvappressureofthesolutionisequalto101.3kPa.TheeffectofanysoluteYontheboilingpointofXwilldependthenuponthenatureofY.IfYislessvolatilethanX.thenthe

10、totalvappressureofthesolutionisloweratanygiventemperaturethanthevappressureofpureX.正常沸點的任何解決方案都是在其溶液總蒸汽壓力等于101.3kPa時的溫度。任何溶質，YNx=X在溶液中的摩爾分數(shù)Similarly.相同的，Py=Py0NywherePy=thepartialpressureofYinsolution.Py=Y在溶液中的分壓Py0=thev

11、appressureofpureYatthattemperaturePy0=純Y在該溫度下的蒸汽壓Ny=themolefractionofyinsolution.Ny=Y在溶液中的摩爾分數(shù)ThetotalpressurePTofthesolutionwouldbethesumofthepartialpressuresofXY.溶液的總壓，PT，是X和Y的分壓的加和。PT=PxPyTemperatureCompositionDiagram

12、fSolutionswhichFollowRaoultsLaw.溶液的溫度—組成圖遵循拉烏爾定律ThesefactsarerepresentedgraphicallyinFig.6whichshowsatypicaltemperaturecompositiondiagram.Thisdiagramisatemperaturecompositionplotoftheexperimentallydeterminedvaluesfthesys

13、tembenzenetoluenebutitisrepresentativeoftheplotfallsolutionswhicharedescribedbyRaoultsLaw.根據(jù)事實，用圖6來表示，圖6是一個典型的溫度組成圖。這個圖是用實驗方法對苯甲苯系統(tǒng)測定值而得到，但對所有可以用拉烏爾定律來表示的溶液，這是一個典型的圖。Boilingpoints(dinates)areplottedagainstcompositionexpr