Reaction of inorganic compound in aqueous solution

• What are the definitions of Lewis acids and bases?

  • Lewis acid: electron pair acceptor
  • Lewis base: electron pair donor
• What is the reaction that occurs when [M(H2O)6]2+ reacts with H2O?

  [M(H2O)5(OH)]+ + H3O+
• Why is the ligand considered a Lewis base in complex ion formation?

  Because it donates a pair of electrons in the dative covalent bond
• Which metal ions correspond to the colors green and blue in [M(H2O)6]2+?

  Fe (green) and Cu (blue)
• What are metal aqua ions formed in aqueous solution?

  [M(H2O)6]2+ and [M(H2O)6]3+
• What color does Fe(III) appear in solution due to hydrolysis reactions?

  Yellow/brown
• Why is the acidity of [M(H2O)6]3+ greater than that of [M(H2O)6]2+?

  Because 3+ metal ions have higher charge density and greater polarising power
• How does polarising power affect the O-H bond in metal aqua ions?

  The greater the polarising power, the more strongly it attracts the water molecule, weakening the O-H bond
• What precipitates are formed when OH- and ammonia react with metal aqua ions in limited amounts?

  M(OH)2(H2O)4 and M(OH)3(H2O)3
• What are the precipitate colors for Cu and Fe(II) when reacting with limited OH- or NH3?

  • Cu: blue precipitate
  • Fe(II): green precipitate
• What is the reaction of [Cu(H2O)6]2+ with OH-?

  [Cu(H2O)6]2+ + 2OH- → Cu(H2O)4(OH)2 + 2H2O
• What is the reaction of [Fe(H2O)6]2+ with NH3?

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

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

  [Fe(H2O)6]3+ + 3NH3 → Fe(H2O)3(OH)3 + 3NH4+
• How does the process of deprotonation occur in metal aqua ions?

  • It can happen stepwise, removing one proton at a time.
  • Example: [Al(H2O)6]3+ + OH- → [Al(H2O)5(OH)]2+ + H2O
• What happens when aluminum hydroxide reacts with excess NaOH?

  It dissolves to form [Al(OH)4]- in a colorless solution
• What occurs when aluminum hydroxide reacts with acids?

  It dissolves to form [Al(H2O)6]3+
• What is the reaction of Al(OH)3 with OH-?

  Al(OH)3 + OH- → [Al(OH)4]- + 3H2O
• What happens when excess NH3 reacts with Cu precipitate?

  A ligand substitution reaction occurs, forming a deep blue solution
• How do NH3 and OH- ions act in the reactions described?

  They act as Bronsted-Lowry bases accepting a proton
• What is the reaction of Cu(OH)2(H2O)4 with NH3?

  Cu(OH)2(H2O)4 + 4NH3 → [Cu(NH3)4(H2O)2]2+ + 2H2O + 2OH-
• What is the reaction of Cu2+ with carbonate solution?

  Cu2+ + CO3^2- → CuCO3 (s)
• What is the reaction of Fe2+ with carbonate solution?

  Fe2+ + CO3^2- → FeCO3 (s)
• How do 2+ and 3+ ions react differently with carbonate solutions?

  • 2+ ions form MCO3 precipitate.
  • 3+ ions form M(OH)3 precipitate and evolve CO2 gas.
• What is the reaction of [Fe(H2O)6]3+ with carbonate solution?


  2[Fe(H2O)6]3+ + 3CO3^2- → 2Fe(OH)3(H2O)3(s) + 3CO2 + 3H2O
• What is the reaction of [Al(H2O)6]3+ with carbonate solution?

  2[Al(H2O)6]3+ + 3CO3^2- → 2Al(OH)3(H2O)3(s) + 3CO2 + 3H2O
• What is the reaction of [Cu(H2O)6]2+ with carbonate solution?

  [Cu(H2O)6]2+ + CO3^2- → CuCO3 + 6H2O
• What is the reaction of [Fe(H2O)6]2+ with carbonate solution?

  [Fe(H2O)6]2+ + CO3^2- → FeCO3 + 6H2O
• What are the colors of the precipitates formed with carbonate solutions for Cu and Fe(II)?

  • Cu: blue/green precipitate
  • Fe(II): green precipitate
• What are the precipitate colors formed with carbonate solutions for Al and Fe(III)?

  • Al: white precipitate of Al(OH)3 + CO2
  • Fe(III): brown precipitate of Fe(OH)3 + CO2
• What is the summary of reactions for 2+ and 3+ ions with hydroxide and carbonate solutions?

  • 2+ ions: form M(OH)2 and MCO3 precipitates.
  • 3+ ions: form M(OH)3 precipitates and evolve CO2 gas.
• What are the colors of the solutions formed by different metal aqua 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 (II) (green ppt)
  • M(OH)3: Fe (III) (brown ppt), Al (white ppt)