lonization Constants of Some Diprotic Acids and a polyprotic Acid and Their Conjugate Bases at 25C Conjugate Name of Acid Formula Structure AbAse K Sulfuric acid H2SO4 ver arge HSO very small Hyc drogen sulfate ion HSO H-0-S-0 13×10-2s0 77×10-13 00 Oxalic acid C2H2O4 H-0-C-C-0—H 6.5×102c2HO4 1.5×10 00 Hydrogen oxalate ion CHO H-0-C-C-0 6.1×10-5c202 1.6×10 Sulfurous acid H2SO3 0-S-0-H 13×10-2Hso 77×10-13 O Hydrogen sulfite ion HSO3 H-0-S-0 63×108SO 1.6×10-7
Molecular Structure and Acid Strength HX→H+X The stronger The weaker the bond the acid Bond Energies for Hydrogen Halides and Acid Strengths for Hydrohalic Acids Bond Bond Energy( kJ/mol) Acid Strength H-F 568.2 weak 431.9 strong H-Br 366.1 strong H-I 2983 ong 3A 5A6A7A F HF<<HCI< HBr< HI
Molecular Structure and Acid Strength Molecular Structure and Acid Strength H X H + + X − The stronger The stronger the bond the bond The weaker The weaker the acid the acid HF << HCl < HBr < HI
Molecular structure and acid strength δ-8 Z-0—H Z-0-+H The o-h bond will be more polar and easier to break if: Z is very electronegative or z is in a high oxidation state O H-0-C-0-H H-0-N=0 Carbonic acid Nitrous acid nitric acid O 0: O H-0-P-0-H H-0-P-O-H H-0-S-0—H O 0: H Phosphorous acid Phosphoric acid Sulfuric acid
Molecular Structure and Acid Strength Molecular Structure and Acid Strength Z O H Z O − + H + δ − δ + The O − H bond will be more polar and easier to break if: H bond will be more polar and easier to break if: ¾ Z is very electronegative or Z is very electronegative or ¾ Z is in a high oxidation state Z is in a high oxidation state
Molecular Structure and Acid Strength 1. Oxoacids having different central atoms(z) that are from the same group and that have the same oxidation number. Acid strength increases with increasing electronegativity of z 0 0 H-0-Cl--0 H-O--Br-Oo ●● ●●●● ● Cl is more electronegative than br 8A A4A5A6A7A c HCIO,> HBrO HHH
Molecular Structure and Acid Strength Molecular Structure and Acid Strength 1. Oxoacids Oxoacids having different central atoms (Z) that are from the same having different central atoms (Z) that are from the same group and that have the same oxidation number. group and that have the same oxidation number. Acid strength increases with increasing Acid strength increases with increasing electronegativity electronegativity of Z Cl is more electronegative than Br is more electronegative than Br • • H O H O Cl O O • • • • • • •• • • • • •• •• • • H O Br O H O Br O O • • • • • • •• • • • • •• •• HClO 3 > HBrO 3
Molecular Structure and Acid Strength 2. Oxoacids having the same central atom (z but different numbers of attached groups. Acid strength increases as the oxidation number of z increases H-0-CI H-0-CI-0: Hypochlorous acid(+1) Chlorous acid (+3) HCIO> HCIO>HCIO,> HCIO :O: :0: H-0-C—0: H-0-C-0: O Chloric acid (+5) Perchloric acid (+7)
Molecular Structure and Acid Strength Molecular Structure and Acid Strength 2. Oxoacids Oxoacids having the same central atom (Z) but different having the same central atom (Z) but different numbers of attached groups. numbers of attached groups. Acid strength increases as the Acid strength increases as the oxidation number of Z increases. oxidation number of Z increases. HClO 4 > HClO 3 > HClO 2 > HClO