2022新陈老师521录入

SketchthephasediagramandLabeleachsubstanceineachregionassolid,liquid,orgasfortheMg/Cusystemusingthefollowinginformation:7y(Mg)=648C,:7y(Cu)=1085C；twointermetalliccompoundsareformedwith7y(MgCu2)=800℃and7y(Mg2Cu)=580℃;eutecticsofmasspercentageMgcompositionandmeltingpoints10percent(690℃),33percent(560℃),and65percent(380℃).AsampleofMg/Cualloycontaining25percentMgbymasswaspreparedinacrucibleheatedto800℃inaninertatmosphere.Describewhatwillbeobservedifthemeltiscooledslowlytoroomtemperature.Specifythecompositionandrelativeabundancesofthephasesandsketchthecoolingcurve.1.利用下列数据，给出Mg—Cu二元合金相图并标出各区相态。Mg(s)和Cu(s)的熔点分别为648c和1085C；两种稳定化合物MgC”和Mg2Cu的熔点为800C和580℃;三个最低共熔点组成和温度分别是:亚乂8(质量百分比，下同)=010,t=690℃,WMg=0.33,t=560℃,WMg=0.65,t=380℃o画出WMg=0.25的合金由800C缓慢冷却至室温的步冷曲线和冷却过程的相变化。TheinformationhasbeenusedtoconstructthephaseidagraminFig.1.InMgCu2themasspercentage=16,ofMgis(100)X24.324.3+127andinMg2Cutheitis(100)X48.648.6+63.5=431Theinitialpointisa1,correspondingtoaliquidsingle-phasesystem.Ata2(at720℃)MgCu2beginstocomeoutofsolutionandtheliquidbecomesricherinMg,movingtowarde2.Ata3thereissolidMgCu2+liquidofcompositione2(33percentbymassofMg).Thissolutionfreezeswithoutfurtherchange.ThecoolingcurvewillresemblethatshowninFig.1.㈤1200-iCuMgCu^ MgTimeFig.1.Inabreathalysertest,a50cm3sampleofaman’sbreathwasbubbledthroughadichromatesolutionat20℃.Theoxidationofthealcoholproduced3.30X10-5molCr(III),thelossofdichromatebeingmeasuredspectrophotometrically.Ifthelawdefineddrunkennessasoccurringwhenthecontentofalcoholinthebloodexceeded0.05weightpercent,determinewhetherthemanwaslegallydrunkornot.Youmayassumethatthepartialpressureofalcoholoverbloodcontaining0.45weightpercentofalcoholat36.9℃is1.00X104Pa.Foruraniumhexafluoridethevaporpressuresforthesolidandliquidaregivenbyln[p(s)/pa]=29.411-5893.5/Tln[p(l)/pa]=22.254-3479.9/TCalculatethetemperatureandpressureofthetriplepoint;Calculate△fusHmand△fusSmofthetriplepoint;Uraniumisusedextensivelyasanuclearfuel,anenrichedfuelcanbepreparedbygaseousdiffusionofthevolatilecompoundUF6,SupposetheUF6vapourisgeneratedbyheatingthesolidat40℃.WhatwillbevapourpressureofUF6inthegaseousphase?Solution:3479.929.411-5893.5/T=22.254----T=337.2=64.0℃,p=152.5kPa△fuSHm=(5893.5-3479.9)X8.314J•mol-1=20.07kJ•mol-1△fuSm=(29.411-22.254)X8.314J•mol-1=59.50J•K-1•mol-1p=39.89kPa设A、B均为挥发性液体。在一定温度下向纯A液体中加入少量B液体形成理想稀溶液。下列说法是否正确？为什么？(1)该溶液的蒸气压必高于纯A的蒸气压；(2)该溶液的凝固点必低于纯A的凝固点(已知溶液凝固时只析出纯固态A)。提示：可从有关图形或依数性的相关公式入手进行讨论。答：(1)不一定，理由如下：因为P=Pa*・XA+kB*XB=PA*+（kB-PA*）XB当kB>p