【化學】高中化學22個易錯知識點（CHEMICALHIGHSCHOOLCHEMISTRY22FALLIBLEPOINTS）1,HYDROXYLISHYDROXYLITLOOKSLIKEAWHOLEOFOHINFACT,THEHYDROXYLGROUPISAGROUPITSONLYAPARTOFTHEMATERIALSTRUCTUREITDOESNTIONIZEWHICHISAHYDROXYLGROUPOFATOMS,ITISANANION,ORSTRONGORWEAKCANIONIZEOUTSO,ISNOTEQUALTOTHEHYDROXYLHYDROXYLFOREXAMPLE,THEOHINC2H5OHISHYDROXYLANDWILLNOTIONIZETWOOHINSULFURICACIDAREALSOHYDROXYLGROUPSASWEALLKNOW,SULFURICACIDCANNOTIONIZEOHINNAOH,MGOH2,FEOH3,CU2OH2CO3INOHISTHEION,IONIZATIONCANCOMEOUT,SOHERECALLEDHYDROXYL2,FE3IONISYELLOWASWEALLKNOW,FECL3SOLUTIONISYELLOW,BUTDOESNOTMEANTHATFE3ISYELLOWNOTHEALKALIFEOH3OFFE3ISAWEAKBASE,ANDTHESALTSSYNTHESIZEDBYITSBINDINGWITHSTRONGACIDIONSWILLHYDROLYZETOPRODUCEREDDISHBROWNFEOH3THEREFORE,THECONCENTRATEDFECL3SOLUTIONISREDDISHBROWN,ANDTHEAVERAGECONCENTRATIONISYELLOW,WHICHINTHEFINALANALYSISISCAUSEDBYTHEHYDROLYSISOFFEOH3THEREALFE3IONISMAUVERATHERTHANYELLOWADDFE3SOLUTIONTOEXCESSACIDTOINHIBITHYDROLYSIS,YELLOWWILLFADE3,AGOHWATERDECOMPOSITIONIFINDMANYPEOPLESAYSOINFACT,THEAGOHINTHESOLUBILITYTABLEIS“,WHICHISCONSIDEREDTOBEWATERDECOMPOSITION,BUTITISNOTBUTTHEAGOHHASAPOORTHERMALSTABILITYANDCANBEDECOMPOSEDATROOMTEMPERATURE,SOTHEAGOHISDECOMPOSEDIMMEDIATELYAFTERMETATHESIS,SOTHATAGOHDOESNOTEXISTATROOMTEMPERATUREWATERHASNOTHINGTODOWITHITIFTHISOPERATIONISPERFORMEDATLOWTEMPERATURES,THEWHITEPRECIPITATEOFAGOHCANBEOBTAINED4,POLYBASICOXYGENACID,SPECIFICISAFEWYUANACID,SEEACIDINTHENUMBEROFHWHATCANTHENUMBEROFHPOLYBASICIONIZATION,ISTOSEEITSSTRUCTUREINTHENUMBEROFHYDROXYLGROUPS,THEHYDROXYLHYDROGENISNOTNONIONIZINGOUTSUCHASPHOSPHITEH3PO3,ITLOOKSLIKETHEREARETHREEH,ITSEEMSTOBETHREEYUANACID,BUTITSSTRUCTUREISTHATTHEREISAHANDAO,RESPECTIVELY,ANDTHECENTRALATOMSAREDIRECTLYLINKED,BUTNOTAHYDROXYLTHEREAREONLYTWOOANDHTHATMAKEUPHYDROXYLGROUPSTHEREFORE,H3PO3ISADICARBOXYLICACIDOFCOURSE,THEREAREOTHERFACTORSTOCONSIDER,SUCHASLEWISACID,H3BO3CANNOTBEEXPLAINEDHERE5,ACIDSALTANDACIDICSOLUTIONONTHESURFACE,THEACIDSALTSOLUTIONISACIDIC,BUTITISNOTINTHEENDWHATISSALT,TODISCUSSTHESITUATION,WHENTHEIONIZATIONDEGREEISGREATERTHANTHEDEGREEOFHYDROLYSIS,ACIDIC,WHENTHEDEGREEOFIONIZATIONISLESSTHANTHEDEGREEOFHYDROLYSIS,ALKALINEIFTHISISASTRONGACIDSALT,BECAUSEITPRODUCEALARGENUMBEROFH,ANDANIONHYDROLYSIS,SOTHEACIDICACIDACIDSALTSOLUTIONBUTTHEWEAKACIDSALT,THENCOMPAREITTOPRODUCETHEHCAPACITYANDTHEDEGREEOFHYDROLYSISOFTHEANIONIFTHEDEGREEOFHYDROLYSISOFTHEANIONISGREATEREG,NAHCO3,NAHS,NA2HPO4,THESOLUTIONISALKALINECONVERSELY,IFTHEANIONHASASTRONGERABILITYTOIONIZEHEG,NAH2PO4,NAHSO3,THESOLUTIONISACIDIC6ANDH2SO4HAVESTRONGOXIDIZINGPROPERTYTHATSNOTRIGHTJUSTADDA“THICK“WORDINTHEFRONTTHATSRIGHTCONCENTRATEDH2SO4EXISTSINTHEFORMOFMOLECULES,ITSOXIDATIONISREFLECTEDINTHEOVERALLMOLECULES,THEH2SO4INSIS6VALENCE,EASYTOGETELECTRONS,SOITHASSTRONGOXIDATIONTHEOXIDATIONOFDILUTEH2SO4ORSO42ISALMOSTNOEVENH2SISNOTOXIDIZED,MUCHLESSOXIDIZEDTHANTHATOFH2SO3ORSO32ITALSOSHOWSTHATTHEOXIDATIONOFTHENONMETALLICOXORADICALISSTRONGERTHANTHATOFTHEHIGHVALENCESTATE,ANDTHEACIDITYOFHCLOISSIMILARTOTHATOFHCLO4THEREFORE,WHENH2SO4HASSTRONGOXIDATION,ITMUSTBERIGOROUS,WITH“THICK“INFRONT7HYDROCHLORICACIDISCOMMONLYKNOWNASHYDROGENCHLORIDEITSEEMSTHATBOTHOFTHEMHAVETHESAMECHEMICALFORMULA,WHICHMAYLEADTOMISUNDERSTANDINGSHYDROCHLORICACIDISCOMMONLYKNOWNASHYDROGENCHLORIDEINFACT,HYDROCHLORICACIDISAMIXTURE,AMIXTUREOFHYDROGENCHLORIDEANDWATERANDHYDROGENCHLORIDEISAPURESUBSTANCE,WHICHISFUNDAMENTALLYDIFFERENTHYDROGENCHLORIDE,DISSOLVEDINWATER,ISCALLEDHYDROGENCHLORIDE,ANDHYDROGENCHLORIDEISCOMMONLYKNOWNASHYDROCHLORICACID8,SOLUBLEINWATERALKALIARESTRONGALKALI,INSOLUBLEINWATERALKALIISWEAKBASEFROMTHECOMMONSTRONGALKALINAOH,KOH,CAOH2ANDCOMMONWEAKBASEFEOH3ANDCUOH2,ITSEEMSTHATTHEALKALISOLUBLEINWATERISSTRONGALKALI,ANDTHEALKALIWHICHISINSOLUBLEINWATERISWEAKINFACT,THEALKALINESTRENGTHOFALKALIANDSOLUBILITYHAVENOTHINGTODOWITH,INWHICHSOLUBLEINWATERALKALI,DONTFORGETAMMONIAWATER,AMMONIAWATERISAWEAKBASEINSOLUBLEINWATERISNOTNECESSARILYAHIGHBASE,LEARNTHEPERIODICRATEINTHISSECTIONALLKNOW,MAGNESIUMANDHOTWATERAFTERTHEREACTIONDROPSOFPHENOLPHTHALEINRED,MGOH2ISNOTWEAK,BUTSTRONG,BUTMGOH2ISINSOLUBLEANDAGOH,LOOK,AGSMETALISSOWEAKTHATAGOHMUSTBEAVERYWEAKBASEINFACT,BYMEASURINGTHEPHVALUEOFAGNO3SOLUTIONNEARNEUTRAL,WECANALSOKNOWTHATAGOHISALSOASTRONGBASE9,WRITEIONEQUATION,STRONGELECTROLYTEMUSTBEREMOVED,THEWEAKSOLUTIONQUALITYMUSTNOTBEDISMANTLEDINAQUEOUSSOLUTION,ITISTRUETHATTHESTRONGELECTROLYTEISCOMPLETELYIONIZEDINWATER,SOITMUSTBEREMOVEDANDTHEWEAKELECTROLYTECANNOTBECOMPLETELYIONIZED,ANDTHEREFOREDOESNOTDISASSEMBLEBUTINNONAQUEOUSSOLUTIONS,ORWHENTHEWATERINTHEREACTIONSYSTEMISSCARCE,ITDEPENDSINSOLIDPHASEREACTIONS,EITHERSTRONGELECTROLYTEORWEAKELECTROLYTE,NOMATTERWHETHERTHEREACTIONISREALIZEDBYIONEXCHANGEORNOT,ITCANNOTBEREMOVEDSUCHAS2NH4CLCAOH2CACL22NH32H2O,THISEQUATIONWILLALLBEREMOVED,THEREFORECANNOTBEWRITTENASTHEIONEQUATIONSOMEEQUATIONSTOSEEASUBSTANTIVERESPONSE,SUCHASCONCENTRATEDH2SO4ANDCUREACTION,WHILETHECONCENTRATIONOFH2SO4IS98,THEREISASMALLAMOUNTOFWATER,SOMEMOLECULESCANALSOBECOMPLETELYIONIZEDINTOHANDSO42,BUTTHEREACTIONBYUSINGSTRONGOXIDATIONOFCONCENTRATEDH2SO4,REFLECTSTHESTRONGOXIDATIONOFH2SO4MOLECULESITISESSENTIALLYINREACTIONOFTHEH2SO4MOLECULE,SOTHEREACTIONCANNOTBEREMOVEDINH2SO4SIMILARLY,THERESULTINGCUSO4ISRAREBECAUSEOFWATERANDISMAINLYPRESENTINMOLECULARFORM,SOITCANNOTBEREMOVEDWHENTHEWEAKSOLUTIONISDISSOLVED,THEWEAKELECTROLYTEISONLYWEAKRELATIVETOTHEWATER,ANDINSOMEOTHERSOLVENTS,ITMAYBECOMEASTRONGELECTROLYTEFOREXAMPLE,CH3COOHISAWEAKELECTROLYTEINWATER,BUTSTRONGELECTROLYTEINLIQUIDAMMONIAWHENTHELIQUIDAMMONIAISUSEDASASOLVENT,THECH3COOHTAKESPARTINTHEIONREACTIONANDTHECH3COOHCANBEREMOVED10,PLASTICHEADDROPPERMUSTBEHIGHERTHANTHETESTTUBEMOUTHTHISVIEWISINCOMPLETE,INSOMEPARTICULARCONDITIONS,SUCHASTHENEEDTOAVOIDEXCESSIVEAIRIMPURITIESINTHEEXPERIMENT,THEREISNONEEDTOMAKETHEHEADDROPPERHIGHERTHANTHETESTTUBEMOUTHTHISEXAMPLEAPPEAREDINHIGHSCHOOLEXPERIMENTS,NAMELY,FEOH2PRODUCTIONEXPERIMENTS,INORDERTOSEETHECLEARWHITEFLOC,OFTENTHEPLASTICHEADDROPPERDEPTHINTOTHELIQUIDLEVEL11,NITRATEIONMUSTSHOWOXIDATIONINFACT,NO3SHOWEDOXIDATIONONLYINACIDICCONDITIONS,WHEREASINALKALINECONDITIONS,OXIDATIONWASNOTINDICATEDFOREXAMPLE,WHENASKEDWHETHERNO3CANCOEXISTWITHSULFURIONS,THEANSWERISYES12,WHITEANDREDPHOSPHORUSARENOTSOLUBLEINWATER,ANDDISSOLVEDINCS2INFACT,DUETOTHECOMPLEXSTRUCTUREOFREDPHOSPHORUSANDLEADINMANYASPECTSESPECIALLYPHYSICALPROPERTIESANDDISPLAYDIFFERENTSUCHASWHITEPHOSPHORUS,DISSOLVEDINORGANICSOLVENTS,INTERMSOFTOXICITY,ETCINTHECUSTODYOFTHEREDPHOSPHORUSWASNOTSOLUBLEINCS213,THEEXOTHERMICREACTIONMUSTBECARRIEDOUTATLOWTEMPERATURE,ENDOTHERMICREACTIONMUSTBEHEATEDASUITABLETEMPERATUREDEPENDSONMANYFACTORS,THEFIRSTISTHEPRICEISSECOND,THIRDISTHECATALYTICEFFICIENCY,OPERATIONDIFFICULTY,FOURTHISTHEENDOTHERMICANDEXOTHERMICREACTIONSAMONGTHEM,THEMOREIMPORTANTISTHEPRICEANDTHECATALYTICEFFICIENCY,ANDWHETHERORNOTTHEOBJECTOFEXOTHERMICISOFTENNOTCONSIDEREDINHIGHSCHOOL,THEMOSTPROMINENTEXAMPLEOFTHISISTHEEXTRACTIONOFAMMONIATHEREACTIONBETWEENN2ANDO2ISANEXOTHERMICREACTION,BUTBECAUSEOFTHEACTIVITYOFTHECATALYST,500DEGREESARECHOSENASTHEPRODUCTIONTEMPERATURE14,MUSTBESTRONGERACIDALKALICANMAKEWEAKACIDALKALITHISISNOTTHECASEWHENTHETEMPERATUREANDPRESSURECHANGE,FOREXAMPLE,THEPRODUCTIONOFSTRONGVOLATILEACIDSISOFTENTHEUSEOFVOLATILEACIDSRATHERTHANTHESTRENGTHOFACIDSIFUNDERNORMALTEMPERATUREANDPRESSURE,ITISNOTNECESSARILYTHECASEINTHEREACTION,IFPRECIPITATIONOROTHERPHENOMENA,OFTENAFFECTTHELAWFOREXAMPLE,ONEOFTHEMOSTNOTABLEEXAMPLESINEACHOTHERBYALKALI,CAOH2BYNAOH15MUSTBESTRONGMETAL,YOUCANREPLACETHEMETALWEAKTHISRULEISOFTENESTABLISHEDIFTHESOLUTIONISEQUALTOTHENORMALTEMPERATURE,BUTTHELAWDOESNOTAPPLYIFTHESTATEOFTHEMETALHASCHANGEDTHEMOSTOBVIOUSEXAMPLEISTHEPRODUCTIONOFTHESTRONGESTMETALCESIUM,CS,WHICHISREPLACEDBYMGFROMCSCLUNDERTHEPROTECTIONOFRAREGASES16,ALLTHEHYDROLYSISPRECIPITATIONISNOTTOOBIGDIFFERENCETHEPRECIPITATIONAREHYDROLYZEDTOPRODUCETHECORRESPONDINGPHVALUERANGELIMIT,THEHYDROLYSISOFFE3CANSTABLYEXISTINPH45,FE2ANDCU2ARENOTITALSOEXPLAINSWHYTHEFE3SOLUTIONWILLAPPEAROBVIOUSPRECIPITATIONINFACT,THISISAMISUNDERSTANDING,ISINSOLUBLEINSOLUTIONISPRECIPITATIONBUTALOTOFTIME,ANDTHEHYDROLYSISOFFE2SOLANDCU2AREGENERALLYSLIGHTLYREACHINGNEUTRALCONDITIONSWASSIGNIFICANT17INTHEREACTIONOFSI,ALANDNAOHSOLUTIONS,NAOHISANOXIDANTINFACT,INTHISREACTION,THEWATEROFTWOMOLECULESISOMITTED,ANDTHEHYDROGENPRODUCEDISDERIVEDFROMWATER,NOTNAOH,SONAOHISONLYANALKALINEENVIRONMENTTHISKNOWLEDGECANCONTINUETOEXPANDTOTHEELEMENTSOFTHETHIRDPERIODANDNAOHREACTIONSOWEMUSTCONSIDERAGAIN,THEOXIDANTORREDUCTANTINTHEENDISWHATIHAVENTIDENTIFIED,PLEASECOMPLETEIT,FOLLOWEDBYNA,MG,AL,SI,P,S,CL18,ASLONGASTHEREISAPALEYELLOWPRECIPITATEISAGBR,ASLONGASTHEREISAREDPRECIPITATEOFFEOH3,ASLONGASTHEREISAGREENSUBSTANCEINTHEPRESENCEOFFE2IONS,ASLONGASTHEREISAPURPLESOLUTIONMUSTBEPOTASSIUMPERMANGANATEANDSOONAYELLOWPRECIPITATEMAYBES/AG3PO4/GOLDASINAQUAREGIADISPLACE/TNT,ANDREDPRECIPITATEMAYBECU2O/COPPER/HGO,GREENMATERIALMAYBETHATIS,PSEUDOMONASAERUGOPURPLESOLUTIONMAYBECCL4SOLUTIONOFIODINE19,THEPRODUCTIONOFCO2INTHEMATERIALMUSTCONTAINTHEEXISTENCEOFCO3ROOTIONS,THEREISPBIONMUSTBENO3SALTBECAUSEYOUTENDTOIGNOREORGANICMATTER,SUCHASOXALICACIDANDACETICACID,INWHATSEEMSTOBEANINORGANICREACTION,ANDTHESEORGANICSUBSTANCESOFTENEXHIBITPROPERTIESSIMILARTOTHOSEOFINORGANICSUBSTANCESWEALW