chapter 20

• generic formula of acid and water

  HA(aq) + H₂O(l) -> H₃O₊(aq) + A₋(aq)
• acids


  proton donors
• bronsted lowry acid


  HA (aq) + water -> H₊(aq) + A₋(aq)
• generic formula of base and acid

  B(aq) + H₂O(l) -> BH₊(aq) + OH₋(aq)
• base

  proton (H+) acceptor
• bronsted lowry base example

  NH3 (aq) + H2O(l) -> NH4+(aq) + OH-(aq)
• strong acids fully dissociate
• weak acids do not fully dissociate
• strength of the acid is determined by the concentration of H3O+(aq) or H+(aq) ion
• high OH- concentration = low H+ concentration
• high OH- and low H+ gives an alkali = high pH
• low OH- and high H+ gives an acid = low pH
• conjugate acid base pairs

  linked by proton (H+) transfer

  
• pH = -log [H+ (aq)]
• monobasic acid

  donate one H+ proton e.g HCl
• diabasicacid

  H2A, donate 2 H+ ions e.g H2SO4
• tribasic acid


  H3A, donate 3 H+ ions, e.g H3PO4
• lowest concentration of H+, highest pH
• to find out H+ conc

  [H+(aq)] = 10 to the power of -pH
• acid dissociation constant

  Ka
• Ka


  equation

  
• the larger the value for Ka, the greater the dissociation
• to find pH from Ka

  pKa = -log[Ka]
• to find Ka from pKa(pH)

  Ka = 10 to the minus power of pKa
• in acids [H+] > [OH-]
• in alkalis [H+] < [OH-]
• dissociation of water

  H2O (l) -><- H+(aq) + OH-(aq)
• in neutral [H+] = [OH-]
• equilibrium of the dissociation of water is on the LEFT
• Kc for dissociation of water 


  equation