化學(xué)專業(yè)英語(yǔ)馬永祥翻譯36課

1、36沸點(diǎn)和蒸餾沸點(diǎn)和蒸餾BoilingPointsofPureLiquids沸點(diǎn)的純液體Anygivenliquidwhenadmittedintoaclosedevacuatedspaceevapatesuntilthevapattainsacertaindefinitepressurewhichdependsonlyuponthetemperature.Thispressurewhichisthepressureexertedbyt

2、hevapinequilibriumwiththeliquidisthevappressureoftheliquidatthattemperature.Asthetemperatureincreases.thevappressureofatypicalliquidxincreasesregularlyasshownbythegeneralizedvappressuretemperaturecurveBCinFig.5.任何給定的液體當(dāng)進(jìn)

3、入一個(gè)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(gè)壓力，是通過(guò)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(gè)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(dá)到101.3kPa。開始煮和xTp被稱為正常沸點(diǎn)液體的x。在這個(gè)溫度，當(dāng)蒸汽壓達(dá)到101.3kPa時(shí)，液體x開始沸騰，這個(gè)蒸汽壓力被叫做x的正常沸點(diǎn)。任何一種液體

6、在它的蒸汽壓達(dá)到101.3kPa之前都不分解，每種液體的沸點(diǎn)都有其自身的特點(diǎn)。一般來(lái)說(shuō)一種物質(zhì)的沸點(diǎn)取決于它的分子質(zhì)量和它們之間的引力的強(qiáng)度。對(duì)于一個(gè)給定的同系物，其成員化合物的沸點(diǎn)隨分子量的增加而增加。Polarliquidstendtoboilhigherthannonpolarliquidsofthesamemolecularweightassociatedpolarliquidsusuallyboilconsiderablyhi

7、gherthannonassociatedpolarcompounds.極性液體的沸點(diǎn)往往高于相同分子量的非極性液體，而相關(guān)的極性液體的沸點(diǎn)遠(yuǎn)遠(yuǎn)高于一般的極性化合物。Theboilingpointisaacteristicconstantthatiswidelyusedintheidentificationofliquids.Becauseofitsmarkeddependenceuponpressureitsrathererratic

8、responsetoimpuritieshoweveritisgenerallylessreliableusefulinacterizationasacriterionofpuritythanisthemeltingpointfsolids1.沸點(diǎn)是一個(gè)常數(shù)廣泛用于識(shí)別液體。然而，由于對(duì)壓力的顯著依賴性和對(duì)雜質(zhì)的相當(dāng)無(wú)規(guī)律的反應(yīng)，沸點(diǎn)用于鑒別和作為純度的判據(jù)方面，較之固體的熔點(diǎn)一般不太可信和較少使用。BoilingPointsofSol

9、utions沸點(diǎn)的解決方案Thenmalboilingpointofanysolutionisthetemperatureatwhichthetotalvappressureofthesolutionisequalto101.3kPa.TheeffectofanysoluteYontheboilingpointofXwilldependthenuponthenatureofY.IfYislessvolatilethanX.thenthe

10、totalvappressureofthesolutionisloweratanygiventemperaturethanthevappressureofpureX.正常沸點(diǎn)的任何解決方案都是在其溶液總蒸汽壓力等于101.3kPa時(shí)的溫度。任何溶質(zhì)，YNx=X在溶液中的摩爾分?jǐn)?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?jǐn)?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(shí)，用圖6來(lái)表示，圖6是一個(gè)典型的溫度組成圖。這個(gè)圖是用實(shí)驗(yàn)方法對(duì)苯甲苯系統(tǒng)測(cè)定值而得到，但對(duì)所有可以用拉烏爾定律來(lái)表示的溶液，這是一個(gè)典型的圖。Boilingpoints(dinates)areplottedagainstcompositionexpr