1. Acids and Bases intro

2. Acid/Base Definitions  Arrhenius Model  Acids produce hydrogen ions in aqueous solutions  Bases produce hydroxide ions in aqueous solutions  Bronsted-Lowry Model  Acids are proton donors  Bases are proton acceptors

3. Acid Dissociation HA  H + + A - Acid Proton Conjugate base Alternately, H + may be written in its hydrated form, H 3 O + (hydronium ion)

4. for example… HCl  H + + Cl - Acid Proton Conjugate base

5. Dissociation of Strong Acids Strong acids are assumed to dissociate completely in solution. Large K a or small K a ? Reactant favored or product favored?

6. Dissociation Constants: Strong Acids AcidFormula Conjugate Base KaKa Perchloric HClO 4 ClO 4 - Very large Hydriodic HI I - Very large Hydrobromic HBr Br - Very large Hydrochloric HCl Cl - Very large Nitric HNO 3 NO 3 - Very large Sulfuric H 2 SO 4 HSO 4 - Very large Hydronium ion H 3 O + H 2 O 1.0

7. Dissociation of Weak Acids Weak acids are assumed to dissociate only slightly (less than 5%) in solution. Large K a or small K a ? Reactant favored or product favored?

8. Dissociation Constants: Weak Acids AcidFormula Conjugate Base KaKa Iodic HIO 3 IO 3 - 1.7 x 10 -1 Oxalic H 2 C 2 O 4 HC 2 O 4 - 5.9 x 10 -2 Sulfurous H 2 SO 3 HSO 3 - 1.5 x 10 -2 Phosphoric H 3 PO 4 H 2 PO 4 - 7.5 x 10 -3 Citric H 3 C 6 H 5 O 7 H 2 C 6 H 5 O 7 - 7.1 x 10 -4 Nitrous HNO 2 NO 2 - 4.6 x 10 -4 Hydrofluoric HF F - 3.5 x 10 -4 Formic HCOOH HCOO - 1.8 x 10 -4 Benzoic C 6 H 5 COOH C 6 H 5 COO - 6.5 x 10 -5 Acetic CH 3 COOH CH 3 COO - 1.8 x 10 -5 Carbonic H 2 CO 3 HCO 3 - 4.3 x 10 -7 Hypochlorous HClO ClO - 3.0 x 10 -8 Hydrocyanic HCN CN - 4.9 x 10 -10

9. Self-Ionization of Water H 2 O + H 2 O  H 3 O + + OH - At 25 , [H 3 O + ] = [OH - ] = 1 x 10 -7 K w is a constant at 25  C: K w = [H 3 O + ][OH - ] K w = (1 x 10 -7 )(1 x 10 -7 ) = 1 x 10 -14

10. Calculating pH, pOH pH = -log 10 (H 3 O + ) pOH = -log 10 (OH - ) Relationship between pH and pOH pH + pOH = 14 Finding [H 3 O + ], [OH - ] from pH, pOH [H 3 O + ] = 10 -pH [OH - ] = 10 -pOH

11. pH and pOH Calculations

12. pH Scale