5.2.1 Ionization equilibrium of water H2O (1)+H2O(1)=HgO*(aq)+OH (aq) or H2O(1)-H(aq)+OH (ag) KC(HO)c(OH) c⊙ ce or K=c(H;O)c(OH) KR 一ion-product constant of water(水的离 子积常数) 25℃：c(H)=c(OH-)=1.0×107molL1 Ke=1.0×10-14 100℃：Ke=5.43×1018T个，Ke个whyV2D
5.2.1 Ionization equilibrium of water H2O (l) + H2O(l) H3O+ (aq) + OH－(aq) or H2O (l) H + (aq) + OH－(aq) — ion-product constant of water (水的离 子积常数） KW 25℃：c(H+ )= c(OH－)=1.0×10-7mol·L-1 100℃： =1.0×10-14 KW =5.43×10-13 KW T ， KW (H O ) (OH ) 3 + - or K = c c W (H O ) (OH ) 3 + - = c c c c KW Why?
11 Anwser: Von't Holf equation R T T 5.2.2 The pH scale (a measure of acidity) pH=-1gic(H,O")} POH=-1gic(OH-) Since K=c(H,O')c(OH )=1.0X101 so -lgc(H')-Igc(OH )=-1gK=14 pH+pOH=pK=14 pH only for the cases of [H+]or [OH-]<1 mol.I-1
pOH = -lg{ (OH )} - c pH lg{ (H O )} 3 = - + c 5.2.2 The pH scale (a measure of acidity) { (H O )}{ (OH )} 1.0 10 14 = 3 = × + - - Since KW c c - lg (H ) - lg (OH ) = -lg =14 + - so c c KW \ pH + pOH = p KW =14 - \ = 1 2 θ r m θ 1 θ 2 1 1 ln R T T H K K Anwser: Von’t Holf equation pH only for the cases of [H+ ] or [OH- ]１mol.l-1
Q?Calculate the pH of a solution of 1.0X10-8mol.dm-3 HCIH,O。 Answer: pH=g0x10-8=8
Q? Calculate the pH of a solution of 1.0×10-8mol.dm-3 HCl/H2O。 Answer： pH=-lg1.0x10-8 = 8
5.3 Equilibrium of ionization for weak acids and bases Ionization of water is ALWAYS involved in acid-base equilibria) 5.3.1 Equilibrium of ionization for monoprotic acids and bases 5.3.2 Equilibrium of ionization for polyprotic acids -5.3.3 Acid-base equilibrium in salt(!?) solution
§ 5.3 Equilibrium of ionization for weak acids and bases 5.3.3 Acid-base equilibrium in salt(!?) solution 5.3.2 Equilibrium of ionization for polyprotic acids 5.3.1 Equilibrium of ionization for monoprotic acids and bases (Note! Ionization of water is ALWAYS involved in acid-base equilibria)
5.3.1 Equilibrium of ionization for monoprotic acids and bases 1.Equilibrium of ionization for monoprotic acids Exercise:Calculate the pH of a solution of HAc with Cinitia=0.1M HAc(aq)+H2O(l)-H3O*(aq)+Ac (aq) Since cK>20 Kw,ionization of H2O can be ignored
1.Equilibrium of ionization for monoprotic acids 5.3.1 Equilibrium of ionization for monoprotic acids and bases HAc(aq)+H2O(l) H3O+ (aq)+Ac－(aq) Exercise: Calculate the pH of a solution of HAc with Cinitial = 0.1M Since cKa 20 Kw , ionization of H2O can be ignored