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1、化学知识点归纳2(理论部分)（Chemicalknowledgeinduction2(theoreticalpart)）Two.TheoreticalpartTheapplicationoflawtothehydrolysisofsalts:Saltionwithwateroutoftheionizationofhydrogenionsorhydroxylionsgeneratedweakelectrolytereactioniscalledhydrolysisofsalts.Itsgeneralrule
2、is:whoisweak,whohydrolysis,whoisstrongerthanothers;thetwoisnothydrolyzed;thetwoweakismorehydrolysis;theweakerthemorehydrolysis.So,inwhatcasesdoyouconsiderthehydrolysisofsalt?1.toanalyzeandjudgetheacidityandalkalinityofsaltsolution,weshouldconsiderhydrolys
3、is.2.thehydrolysisofsaltshouldbetakenintoaccountwhendeterminingthespeciesandconcentrationofionsinthesaltsolution.SuchasNa2Ssolutioncontainsions,accordingtotheconcentrationfromlargetosmallorder:C(na+),>c(s2-),>c(oh-),>c(hs-),>c(h+)Or:C(na+),+c(h+),=2c(s2-)
4、,+c(hs-),+c(oh-)3.thehydrolysisofsaltshallbetakenintoconsiderationwhenpreparingcertainsaltsolutionsSuchasthepreparationofFeCl3,SnCl4,Na2SiO3andothersaltsolution,theyshouldbedissolvedinthecorrespondingacidoralkalisolution.4.hydrolysisshouldbeconsideredwhen
5、preparingcertainsaltsAl2S3,MGS,Mg3N2andothersubstancesareveryeasytointeractwithwater.Theycannotexiststablyinsolution.Therefore,theycannotbepreparedbythemethodofdoubledecompositionreaction,butcanonlybepreparedbydryprocess.5.certainreactivemetalsreactwithst
6、ronglyacidweakbasesandconsiderhydrolysisReactivemetalssuchasMg,Al,Zn,etc.reactwithNH4Cl,CuSO4,AlCl3andothersolutions3mg+2alcl3+6h2o=3mgcl2+2al(OH):+3h2=36.todeterminetheacidityandbasicityofthesolutionattheendoftheneutralizationtitration,toselecttheindicat
7、orandtojudgetheexcessoftheacidorbaseintheph=7,thehydrolysisofthesaltshallbetakenintoaccountIfCH3COOHandNaOHreactexactlywhenph>7,ifthetwoisph=7afterreaction,thenCH3COOHisexcessive.Thegeneralprincipleofindicatorselectionisthattherangeofdiscolorationofthesel
8、ectedindicatorshouldbeconsistentwiththerangeofpHvaluesofthesaltsolutionobtainedaftertitration.Thestrongandweakinteractionshouldchoosedropsofmethylorange;weakacidandalkalidropsofphenolphthaleinshouldchooseeachother.7
