实验设计氯化铵的制备

TheProductionofNH4ClPurposes(1)tomastersomefundamentaloperationofperforminganexperiment.(2)toconfirmtherelationofthesolubilityofsaltandtemperature.(3)tomasterthemethodtodeterminethepercentageyieldofnitrogen.Principles(1)2NaCl+(NH4)2SO4⇋Na2SO4+2NH4Cl(2)solubilitydataT/℃0102030405060708090100NaCl35.735.83636.236.536.837.337.638.138.639.2(NH4)2SO470.67375.4788184.88891.695.399.2103.3Na2SO4·10H2O4.79.120.441///////Na2SO4///49.748.246.745.244.143.342.742.3NH4Cl29.733.337.241.445.850.455.260.265.671.377.3(3)NH4Cl~(NH4)2SO453.5u~66u20g~25gm[(NH4)2SO4]=M[(NH4)2SO4]×m(NH4Cl)/M(NH4Cl)=66×20/53.5≈25(g)(4)NH4Cl~NaCl53.5u~58.5u20g~22gm(NaCl)=M(NaCl)×m(NH4Cl)/M(NH4Cl)=58.5×20/53.5≈22(g)(5)Basedonthesolubilitydata,thewaterneededshouldjustdissolve22gNaCland25g(NH4)2SO4Whenthetemperatureis20℃,NaCl~H2O36g~100g22g~61gV(H2O)=m′(H2O)/ρ(H2O)=m(H2O)×m′(NaCl)/[m(NaCl)×ρ(H2O)]≈61mL(NH4)2SO4~H2O75.4g~100g25g~33gV(H2O)=m′(H2O)/ρ(H2O)=m(H2O)×m′[(NH4)2SO4]/﹛m[(NH4)2SO4]×ρ(H2O)﹜≈33mL61mL33mLSoabout61mLdistilledwaterisneededtodissolvethesalt.ToensurethatNaClcandissolvecompletely,weshouldadd70mL~80mLdistilledwaterintothebeaker(6)themixedsolutionshouldbeheateduntilthesolutionisabout65mL-toavoidthecrystallizationofNaCl.BecausethesolubilityofNa2SO4decreaseswhentemperaturegoesup,sowhenthesolutionisheated,Na2SO4crystallizes.(7)thesolutionshouldbecooledtoabout33℃becausethesolubilityofNa2SO4·10H2OandNa2SO4areboththehighestatabout32.4℃accordingtothesolubilitydata.ThentheywouldnotmixwithNH4Cl.(8)themethodoftheexaminationofNH4Clisheating.NH4ClNH3↑+HCl↑WecanseethatpureNH4Clcanbeturnedintogasandhavenosolidleftwhenheated.Thepossibleimpuritycannotbeturnedintogasbythisway.SothisisthemethodtodeterminethepurityofNH4Cl.Thesketchofproceduresbeingheatedandstirredtodissolvebeingbathheated,stirredtodissolve22gNaCl70mL~80mLdistilledwater25gNH4ClNaClsolutionNa+Cl-NH4+SO42-beingcooledtoabout33℃andfilteredbysuctionfiltrationbeingbathheated,stirredandfilteredbysuctionfiltrationbeingcooledtoabout33℃andfilteredbysuctionfiltrationbeingbathheated,stirredandfilteredbysuctionfiltrationbeingcooledtoabout33℃andfilteredbysuctionfiltrationbeingweighedMaterialsdistilledwater,NaCl,(NH4)2SO4beaker,glassrod,Erlenmeyerflask,Buchnerfunnel,suctionflask,Bunsenburner,tripod,graduatedcylinder,spatula,weightingpaper,filterpaper,scale,match,thermometerProcedures(1)weigh22gNaClandmeasure70mL~80mLdistilledwater,thenmixtheminabeaker.(2)heatthebeakerwhilestirringtodissolveNaCl.(3)weigh25g(NH4)2SO4andadditintothebeaker.(4)heatthebeakerbybathheatingwhilestirring.(5)markthebeakerbytheplaceof65mL.Na+,Cl-,NH4+,SO42-Na2SO4↓Na+,Cl-,NH4+,SO42-NH4Cl↓Na+,Cl-,NH4+,SO42-Na+,Cl-,NH4+,SO42-Na+,Cl-,NH4+,SO42-Na+,Cl-,NH4+,SO42-Na2SO4↓Na2SO4↓NH4Cl↓NH4Cl↓beingbathheated,stirredandfilteredbysuctionfiltrationNH4Cl(6)concentratethesolutiontoabout65mL.(7)filterthemixturebysuctionfiltrationwhenthemixtureisstillhot.(8)coolthefiltratetoabout33℃.(9)filerthefiltratebysuctionfiltrationandcollecttheprecipitate.(10)repeatprocedure(7)to(9)twotimes.(11)weightheprecipitateandcalculate.PointsforAttention(1)beforefilteringthemixturebysuctionfiltrationwhenthemixtureisstillhot,therelatedinstrumentsshouldbeheated(2)thevolumeofthedistilledwateraddedindoesn'tequaltothevolumeofthesolution.(3)themarkof65mLonthebeakershouldbemadepreviously.References(1)《氯化铵的制备及氮含量的测定》，(2)FundamentalChemistryExperiments,H.Liu,J.Shi,X.Zou.January,2008edition,SciencePress(3)《实验八设计实验——氯化铵的制备》