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ID:39164517
大小:2.18 MB
页数:83页
时间:2019-06-26
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1、酸碱解离平衡Acids&Bases4第四章第1节酸碱理论概述一Arrhenius酸碱理论二Bransted&lowrey酸碱质子理论三Lewis酸碱电子理论四酸碱溶剂体系理论定义酸:凡是在水中电离产生H+的物质。碱:凡是在水中电离产生OH+的物质。局限性:酸碱物质;酸碱反应;溶剂的影响。一Arrhenius酸碱理论二酸碱质子理论定义酸:凡是能给出质子的物质。碱:凡是能结合质子的物质。酸给出质子后变为碱;碱接受质子变为酸。WhenanHClmoleculedissolvesinwater,ahydrogenbondformsbe
2、tweentheHatomofHCl(theacid)andtheOatomofaneighboringH2Omolecule(thebase).ThenucleusofthehydrogenatomispulledoutoftheHClmoleculetobecomepartofahydroniumion.(1)Asubstancecanactasanacidonlyifabaseispresenttoacceptitsacidicprotons.(2)Anaciddoesnotsimplyreleaseitsacidicp
3、roton:theprotonistransferredtothebasethroughdirectcontact.Forexample,HClisaBrønstedacid.Inthegasphase,anHClmoleculeremainsintact.However,whenHCldissolvesinwater,eachHClmoleculeimmediatelytransfersanH+iontoaneighboringH2Omolecule,whichhereisactingasabase.Thisprocessi
4、saprotontransferreaction,areactioninwhichaprotonistransferredfromonespeciestoanother.WesaythattheHClmoleculebecomesdeprotonated:HCl(aq)+H2O(l)H3O+(aq)+Cl-(aq)Astrongacidisfullydeprotonatedinsolution.AweakacidisonlypartlydeprotonatedinsolutionWhenanoxideionispresenti
5、nwater,itexertssuchastrongattractiononthenucleusofahydrogenatominaneighboringwatermoleculethatthehydrogenionispulledoutofthemoleculeasaproton.Asaresult,theoxideionformstwohydroxideions.酸H++碱-++AcHHAc-+-+2442HPOHPOH-+-+3424POHHPO+++34NHHNH[]+++2333NHCHHNHCH++++252362
6、O)Fe(OH)(HHO)Fe(H[][]++++422252O)(HFe(OH)HO)Fe(OH)(H[][]共轭酸碱统一在同一体系中质子的传递上。共轭酸碱对Theconjugateacidofabaseistheacidthatformswhenthebasehasacceptedaproton.Astrongacidisfullydeprotonatedinsolution;aweakacidisonlypartiallydeprotonatedinsolution.Astrongbaseiscompletelyprot
7、onatedinsolution;aweakbaseisonlypartiallyprotonatedinsolution.酸和碱的强度是指酸给出质子的能力和碱接受质子的能力的强弱。酸越强,其共轭碱越弱;碱越强,其共轭酸越弱。三Lewis酸碱电子理论Lewis酸:凡是可以接受电子对的分子、离子或原子,如Fe3+,Fe,Ag+,BF3等;Lewis碱:凡是给出电子对的离子或分子,如:X-,:NH3,:CO,H2O:等。lewis酸与lewis碱之间以配位键结合生成酸碱加合物。Theblackcurvedarrowsshowthe
8、directioninwhichtheelectronscanbethoughttomove;theredcurvedarrowshowstheprotontransfer.ManynonmetaloxidesareLewisacidsthatreactwithwaterto
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