《无机化学简明教程》课件_Chapter 3 Chemical Equilibium.pptVIP

3.2EffectofchangesinpressureChangingthepressuredoesnotchangethevalueoftheequilibriumconstant.Example5：N2(g)+3H2(g)=2NH3(g)Whenthetotalpressureistwotimesoftheoriginalpressure,Equilibriumwillshifttotheright.Example6:CO(g)+H2O(g)=CO2(g)+H2(g)Whenthetotalpressureistwotimesoftheoriginalpressure,例1：合成氨N2(g)+3H2(g)=2NH3(g)原料气（Air）循环使用，当惰气和积累过多时，影响氨的生成，此时，需放空，补充新鲜气例2：乙烷裂解制乙烯C2H6(g)=C2H4(g)+H2(g)恒T、P时，采用加入H2O(g.)的方法提高乙烯的产率。3.3Effectofchangesintemperature?∵△rGmo（T）=△rHmo－T△rSmo△rGmo（T）=－RT㏑Ko∴－RT㏑Ko=△rHmo－T△rSmo㏑Ko=[－△rHmo（298K）/RT]+[△rSmo（298K）/R]△rHmo0，T2T1，Ko2Ko1△rHmo0，T2T1，Ko2Ko1Toincreasethetemperature,reactionwillshifttotheendothermicreaction.Example7:Calculate:（1）△rGmat427℃（700K）forthereactionN2（g）+3H2(g)→2NH3(g)IfPN2=33.0atm，PH2=99.0atm，andPNH3=2.0atm,(△rHmo=－92.22KJ/mol，△rSmo=－198.53J/mol·K，△rGmo=－32.96KJ/mol)predictthedirectionofspontaneouschange.（2）Ko（298K）,Ko（700K）,Ko（773K）（3）Discussthesuitablereactionconditions.△rGm=△rGmo+RT㏑Q=46.75+8.314×700×10－3㏑=46.75+8.314×700×10－3㏑=46.75+5.82×(－15.896)=46.75－92.51=－45.76(KJ/mol)0Solution：(1)△rGmo(700K)=△rHmo－T·△rSmo=－92.22－700×(－198.53×10－3)=46.7I5(KJ/mol)0Theforwardreactionisnonspontaneousunderstandardstate.Theforwardreactionisspontaneous.lgK773o?lgK298o=?(2)∵△rGmo=RT㏑Ko∴㏑Ko（298K）=13.30Ko(298K)=5.99×105㏑Ko(700K)=－8.30∴Ko(700K)=3.05×10－4Ko（773K）=7.0×10－5△rHmo0，increaseT↑，Kodecreases.?(3)Lowtemperatureandhighpressurewillbehelpfulfortheforwardreaction.However,whenthetemperatureisbelow673K，thereactionspeedisveryslow，whilehightemperaturewillcausedissociationofNH3.Thus，thepracticalreactionconditionis300×105Pa-700×105Pa，773K，withacatalystofiron.?KeyWordsandConceptsReversiblereactionforwardreaction