Acids and Bases

HAVE YOU SEEN THIS MAN?

 

Johannes Brönsted

part time chemist, part time serial killer

 

Last known activity

Basically accepting protons

 Three Theories:

                I. Arrhenius Model

§          Acids produce H+ ions

§         Bases produce OH- ions

                II. Bronsted-Lowry Model

§         Acids = Proton donors (form H3O+ Hydronium ion)

§         Bases = Proton acceptors

III. Lewis Acid-Base Model

§         Acids = e- pair acceptors

§         Bases = e- pair donors

IV. Conjugate Acid-Base Pairs

§         Conjugate base is what’s left after proton is donated from acid

§         Example: H2SO4 (Acid) + H2O (Base) → H3O+ (C.A.)+ HSO4- (C.B.)

pH & pOH:

  • pH = -log ([H+]), pOH = -log ([OH-])
  • pH + pOH = 14
  • Kw = [H+][OH-] = (1.0x10-7) (1.0x10-7) = 1.0x10-14

Dissociation:

  • % dissociation = (amount dissociated (M)) / (initial concentration (M)) * 100%
  • K = [Products] / [Reactants]
  • Example of dissociation of HA: Ka = ([H+][A-]) / [HA]
  •  

Acids:

  • Common strong acids: HCl, HBr, HI, H2SO4, HNO3, HClO4
  • Nonmetal oxides form acids when they react with water
  • Strong acids are associated with weak conjugate bases

Bases:

  • All Group 1A & Group 2A are strong except Mg(OH)2 and Be(OH)2
  • Metallic oxides of Group 1A and 2A form bases when they react with water
  • Strong bases are associated with weak conjugate acids

Terms:

  • Monoprotic – one acidic proton (HCl)
  • Diprotic – two acidic protons (H2SO4)
  • Triprotic – three acidic protons (H3PO4)
  • Oxyacids – acids in which the acidic proton is attached to an oxygen
  • Organic acids – contain carboxyl group (usually weak)

Titrations:

  • Often used to determine the pH of a solution
  • If titrating base with acid: indicator with color change pH of +1 of pKa
  • If titrating acid with base: indicator with color change pH of -1 of pKa