1. Conjugate Acid-Base Pairs

2. Acid Dissociation Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 280 HCl Conjugate base Acid Conjugate pair + 1- Cl H

3. Conjugate Acid-Base Pairs HCl + H 2 O H 3 O + + Cl - acidbase acid conjugates HCl + H 2 O H 3 O + + Cl - acid base CA CB

4. Conjugate Acid-Base Pairs NH 3 + H 2 O NH 4 1+ + OH - baseacid base conjugates base acid CA CB NH 3 + H 2 O NH 4 1+ + OH -

5. Water is Amphoteric base acid CA CB NH 3 + H 2 O NH 4 1+ + OH - HCl + H 2 O H 3 O + + Cl - acid base CA CB Amphoteric or Amphiprotic substances Amphoteric or Amphiprotic substances: Substances which can act as either proton donors (acids) or proton acceptors (bases) depending on what substances are present.

6. Amphoteric 1- ++ sulfuric acid H 2 SO 4 water H2OH2O hydrogen sulfate ion HSO 4 - hydronium ion A substance that can act as either an acid or a base. H3O+H3O+ 1+ 1- ++ sulfate ion SO 4 2- water H2OH2O hydrogen sulfate ion HSO 4 - hydroxide ion OH - 1- 2-

7. 1- + + 1+ sulfuric acid H 2 SO 4 water H2OH2O hydrogen sulfate ion HSO 4 - hydronium ion H3O+H3O+ (HSO 4 - as a base) Amphoteric A substance that can act as either an acid or a base.

8. Amphoteric A substance that can act as either an acid or a base. 1- + hydrogen sulfate ion HSO 4 - hydroxide ion OH - 1- + sulfate ion SO 4 2- water H2OH2O 2- (HSO 4 - as an acid)

9. Conjugate Acid-Base Pairs HC 2 H 3 O 2 + H 2 O H 3 O 1+ + C 2 H 3 O 2 OH - acid 1 base 1 base 2 acid 2 conjugates acid base CA CB HC 2 H 3 O 2 + H 2 O H 3 O 1+ + C 2 H 3 O 2 OH - The reaction proceeds in the direction such that the stronger acid donates its proton to the stronger base.