Reactions of Aqueous Ions

• What is the reaction of [M(H2O)6]2+ with water?

  [M(H2O)5(OH)]+ + H3O+
• What defines a Lewis acid?

  Electron pair acceptor
• What defines a Lewis base?

  Electron pair donor
• In complex ion formation, what role does the ligand play?

  It acts as a Lewis base
• What are metal aqua ions formed in aqueous solution?

  [M(H2O)6]2+ and [M(H2O)6]3+
• Which metal ions correspond to [M(H2O)6]2+ and their colors?

  Fe (green) and Cu (blue)
• Which metal ions correspond to [M(H2O)6]3+ and their colors?

  Al (colorless) and Fe (violet)
• Why does Fe(III) appear yellow/brown in solution?

  Due to hydrolysis reactions
• How does the acidity of [M(H2O)6]3+ compare to [M(H2O)6]2+?

  [M(H2O)6]3+ is more acidic
• What causes the greater acidity of [M(H2O)6]3+?

  Higher charge density and polarising power
• What happens to the O-H bond in [M(H2O)6]3+?

  It weakens and breaks more easily
• What precipitates form with limited OH- and NH3?

  M(OH)2(H2O)4 and M(OH)3(H2O)3
• What are the precipitate colors for Cu and Fe with limited OH-?

  • Cu: blue ppt (Cu(OH)2(H2O)4)
  • Fe(II): green ppt (Fe(OH)2(H2O)4)
• What are the precipitate colors for Fe(III) and Al with limited OH-?

  • Fe(III): brown ppt (Fe(OH)3(H2O)3)
  • Al: white ppt (Al(OH)3(H2O)3)
• What is the reaction of [Cu(H2O)6]2+ with OH-?

  Cu(H2O)4(OH)2 (s) + 2H2O (l)
• What is the reaction of [Al(H2O)6]3+ with OH-?

  Al(H2O)3(OH)3 (s) + 3H2O (l)
• What is the reaction of [Fe(H2O)6]2+ with NH3?

  Fe(H2O)4(OH)2 (s) + 2NH4+
• What is the reaction of [Fe(H2O)6]3+ with NH3?

  Fe(H2O)3(OH)3 (s) + 3NH4+
• How does the deprotonation process occur?

  It can happen stepwise, removing one proton
• What is the reaction of Al(OH)3 with OH-?

  [Al(OH)4]- (aq) + 3H2O (l)
• What happens to aluminium hydroxide with excess NaOH?

  It dissolves to form [Al(OH)4]-
• Why is aluminium hydroxide classified as amphoteric?

  It reacts with both acids and bases
• What is the reaction of Al(OH)3 with H+?

  [Al(H2O)6]3+ (aq)
• What occurs with excess NH3 and Cu?

  A ligand substitution reaction occurs
• What is the product of Cu with excess NH3?

  [Cu(NH3)4(H2O)2]2+
• What happens to the precipitate of Cu with excess NH3?

  It dissolves to form a deep blue solution
• How do NH3 and OH- act in the reactions?

  As Bronsted-Lowry bases accepting protons
• What role does NH3 play in the reactions?

  It acts as a Lewis base donating an electron pair
• How do 2+ ions react with carbonate solutions?

  They form MCO3 precipitates
• How do 3+ ions react with carbonate solutions?

  They form M(OH)3 precipitates and evolve CO2
• Why do 3+ ions not form M2(CO3)3?

  Due to greater polarising power of 3+ ions
• What precipitate forms with Al and carbonate solution?

  White ppt of Al(OH)3
• What precipitate forms with Fe(III) and carbonate solution?

  Brown ppt of Fe(OH)3
• What is the reaction of Fe2+ with carbonate solution?

  FeCO3 (s)
• What is the reaction of [Fe(H2O)6]3+ with carbonate solution?


  2Fe(OH)3(H2O)3(s) + 3CO2 + 3H2O(l)
• What is the reaction of [Al(H2O)6]3+ with carbonate solution?

  2Al(OH)3(H2O)3(s) + 3CO2 + 3H2O(l)
• What is the reaction of [Cu(H2O)6]2+ with carbonate solution?

  CuCO3 + 6H2O
• What is the reaction of [Fe(H2O)6]2+ with carbonate solution?

  FeCO3 + 6H2O
• What are the colors of the solutions for [M(H2O)6]2+ and [M(H2O)6]3+ ions?

  • [Cu(H2O)6]2+: blue solution
  • [Fe(H2O)6]2+: green solution
  • [Al(H2O)6]3+: colorless solution
  • [Fe(H2O)6]3+: yellow solution
• What are the precipitate colors for M(OH)2 and M(OH)3?

  • M(OH)2: Cu (blue ppt), Fe (green ppt)
  • M(OH)3: Fe (brown ppt), Al (white ppt)