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1、Chapter 4 Acid-base equilibria(1)Acid-base proton conceptsThe acid and base of solution are usually expressed by pH value pH 7 basic solutionThe ionization theory(1884,Arrhenius):The compounds whose positive ions are all H+during dissociation is named as acid The compound whose negative ions are all
2、 HO-during dissociation is named as base4.1 Overview of acid-base proton theory(1)It cannot explain that NaCO3,Na3PO4 present the basic property;but NH4Cl shows the acidic property.(2)The acid-base behavior in nonaqueous solutions cannot be interpreted.Obvious limitations：Acid:Substance that can don
3、ate proton(molecule or ion)Base:Substance that can accept proton(molecule or ion)Proton acceptorProton donor Acid-base proton theory:(proton transfer theory,1923)In aqueous solution:HCl(aq)=Cl-(aq)+H+(aq)HAc(aq)=Ac-(aq)+H+(aq)NH4+(aq)=NH3(aq)+H+(aq)H2PO4-(aq)=HPO42-(aq)+H+(aq)Acid and its correspond
4、ing base are interdependent:Acid =proton +base The base formed after the acid loses its proton is names as conjugated base The base combines with protons to form acid,which is named as conjugated acidAl(H2O)63+Al(H2O)5(OH)2+H+acid base protonHPO42 PO43+H+acid base protonHCl,HAc,NH4+,H2SO3,Al(H2O)6 3
5、+,and so on,which donate proton，belong to acid.OH-,Ac-,NH3,HSO3-,CO32-,and so on,which accept proton，belong to base.Increased aciditySome common conjugated acid base pairs acid =base +proton HCl(aq)=Cl-(aq)+H+(aq)H3O+(aq)=H2O +H+(aq)HSO4-(aq)=SO42-+H+(aq)H3PO4(aq)=H2PO4-+H+(aq)HAc(aq)=Ac-(aq)+H+(aq)
6、H2CO3(aq)=HCO3-+H+(aq)H2PO4-(aq)=HPO42-(aq)+H+(aq)NH4+(aq)=NH3(aq)+H+(aq)Increased basicityAmphoteric substance:Molecules or ions can act either as a proton donor or proton acceptorHPO42 PO43+H+Acid base protonH2PO4 HPO42+H+Acid base proton Acids and bases can be molecules or ions Ac-:ionic base，:io
7、nic acid Amphoteric substance No salt formation.Compared with Arrhenius ionization theory,acids and bases are conjugated to each other.:ionic acid，Cl-:conjugated base.Characteristics of Bronsted-Lowery Theory:(2)The essence of acid-base reaction through proton acid-base theory:A proton transfer process between acid and its conjugated base.H+acid(1)base(2)acid(2)base(1)(1)The ionization of acid or baseH+(2)The neutralization of acid or baseH+(3)The hydrolysis of saltH+
