第二章后習(xí)題答案習(xí)題水在20℃時的飽和蒸氣壓為2.34kPa。若于100g水中溶有10.0g蔗糖(Mr解根據(jù),甲溶液由1.68g蔗糖(Mr=342)和20.00g水組成，乙溶液由2.45g（Mr=690）的某非電解質(zhì)和20.00g水組成。⑴ 在相同溫度下，哪份溶液的蒸氣壓高？⑵ 將兩份溶液放入同一個恒溫密閉的鐘罩里，時間足夠長，兩份溶液濃度會不會發(fā)生變化，為什么？⑶ 當(dāng)達(dá)到系統(tǒng)蒸氣壓平衡時，轉(zhuǎn)移的水的質(zhì)量是多少？解(1)溶液乙的蒸氣壓下降小，故蒸氣壓高。（2）乙溶液濃度變濃,甲溶液濃度變稀。因為濃度不同的溶液置于同一密閉容器中，由于不同，P不同，蒸發(fā)與凝聚速度不同。乙溶液蒸氣壓高，溶劑蒸發(fā)速度大于甲溶液蒸發(fā)速度，所以溶液乙中溶劑可以轉(zhuǎn)移到甲溶液。（3）設(shè)由乙溶液轉(zhuǎn)移到甲溶液的水為x(g),當(dāng)兩者蒸氣壓相等時，則x=3.22g3. 將2.80g難揮發(fā)性物質(zhì)溶于100g水中，該溶液在101.3kPa下，沸點為100.51℃。求該溶質(zhì)的相對分子質(zhì)量及此溶液的凝固點。(Kb=0.512K·kg·mol-1，Kf=1.86K·kg·mol-1解該溶液的凝固點為-1.85℃4. 煙草有害成分尼古丁的實驗式是C5H7N，今將538mg尼古丁溶于10.0g水，所得溶液在101.3kPa下的沸點是100.17℃解尼古丁的分子式為：5.溶解3.24g硫于40.0g苯中，苯的凝固點降低1.62℃。求此溶液中硫分子是由幾個Solution:（a）(b)2.If4.00gofacertainnonelectrolyteisdissolvedin55.0gofbenzene,theresultingsolutionfreezesat2.36℃.Calculatethemolecularweightofthenonelectrolyte.Solution:3.Theaverageosmoticpressureofseawaterisabout30.0atmat25℃.Calculatetheconcentration(molarity)ofanaqueoussolutionofurea(NH2CONH2)thatisisotonicwithseawater.Solution:4.Aquantityof7.85gofacompoundhavingtheempiricalformulaC5H4isdissolved301gofbenzene.Thefreezingpointofthesolutionis1.05℃belowthatofpurebenzene.Whatarethemolarmassandmolecularformulaofthiscompound?Solution:Sincetheformulamassofisandthemolarmassisfoundtobe,themolecularformulaofthecompoundis.5.Ethyleneglycol(EG)CH2(OH)CH2(OH),isacommonautomobileantifreeze.itischeap,water-soluble,andfairlynonvolatile(b.p.197℃).Calculatethefreezingpointofasolutioncontaining651gofthissubstancein2505gofwater.Wouldyoukeepthissubstanceinyourcarradiatorduringthesummer?Themolarmassofethyleneglycolis62.01g.Solution:M(EG)=62.01g·mol-1Becausethesolutionwillboilat102.15℃,itwouldbepreferabletoleavetheantifreezeinyourcarradiatorinsummertopreventthesolutionfromboiling.6.Asolutionispreparedbydissolving35.0gofhemoglobin(Hb)inenoughwatertomakeuponeliterinvolume.Iftheosmoticpressureofthesolutionisfoundtobe10.0mmHgat25℃Solution:theconcentrationofthesolution:7.A0.86percentbymasssolutionofNaCliscalled“physiologicalsaline”becauseitsosmoticpressureisequaltothatofthesolutioninbloodcell.Calculatetheosmot