Acid/Base Arrhenius definition acid produces H+ in water base produces OH- in water  HA + H2O   H+ + A- Ka = [H+] [A-] Ka strength of acid [HA] [H2O] [HA] strong acids no Ka weak acids dissociate completely equilibrium process HCl, HBr, HI HF Ka = 6.8 x 10-4 HNO3, HClO4, H2SO4 HIO3 Ka = 0.16

Acid/Base Arrhenius definition acid produces H+ in water base produces OH- in water NaOH (s) + H2O  Na+(aq) + OH- (aq) NH3 (g) + H2O  NH4+ (aq) + OH- (aq) strong bases weak bases Kb OH- Group I NH3 Kb = 1.8 x 10-5 Group II O2- R-NH2 amines (Ca, Sr, Ba)

Brønsted-Lowry Acids and Bases proton donor H .. base proton acceptor O H .. .. O H + H Cl + Cl-  + conjugate pair base acid strong acid very weak base conjugate pair stronger acid stronger base +

Brønsted-Lowry Acids and Bases strength of acid related to stability of conjugate base conjugate bases carry negative charges stabilized by: polarizability related to size (LDF) electronegativity inductive effect resonance e- in HI  H+ + I- 5p orbital largest orbital most stable HBr  H+ + Br- 4p orbital HCl  H+ + Cl- 3p orbital strongest acid HF  H+ + F- 2p orbital

Brønsted-Lowry Acids and Bases strength of acid related to stability of conjugate base conjugate bases carry negative charges stabilized by: electronegativity with same size orbitals, electronegativity determines stability F- OH- NH2- CH3- HF > H2O > NH3 > CH4

Brønsted-Lowry Acids and Bases strength of acid related to stability of conjugate base conjugate bases carry negative charges inductive effect related to electronegativity – but atom near charge more stable base stronger acid

Brønsted-Lowry Acids and Bases strength of acid related to stability of conjugate base conjugate bases carry negative charges resonance HNO3 HNO2 For oxoacids with same central atom, more O means stronger acid For oxoacids with same number of O, more electronegative central atom means stronger acid

Brønsted-Lowry Acids and Bases proton donor base proton acceptor N H + N H .. O H .. .. O H - +  + acid base base acid weak base relatively strong acid Kb = 1.8 x 10-5

Autoionization of H2O H H2O  H+ (aq) > + OH- (aq) Kw = [H+] [OH-] = 1.0 x 10-14 at 25oC [H+] [H2O] = [OH-] 55.5 M = 1.0 x 10-7 - 0.0000001 Kw = [0.1] [OH-] = 1.0 x 10-14 [OH-] = 1.0 x 10-13 Le Chatelier add H+ [OH-] decrease 0.10 mol HCl = 0.1 mol H+ [H+] = 0.10 M 1.0 L L both present in all aqueous solutions

pH [H+] 10 M - 10-15 M pH = - log [H+] low pH -1 15 high pH acidic basic neutral [H+] = [OH-] = 1.0 x 10-7 pH = 7 pOH = - log [OH-] pH + pOH = 14 pH of milk = 6.4 [H+] = 3.981071706 x 10-7 -6.4 10 4 x 10-7 1 sig. fig.

Brønsted-Lowry Acids and Bases proton donor base proton acceptor C2H3OOH + CN-  C2H3OO- + HCN acid base base1 acid2 1 2

Brønsted-Lowry Acids and Bases proton donor base proton acceptor HF + H2O  Ka = 7.2 x 10-4 F- + H3O+ acid1 base2 base1 acid2 CH3NH2 + H2O  CH3NH3+ + OH- base1 acid2 acid1 base2 H3O+ strongest acid in water H2O amphoteric OH- strongest base in water acid or base