Mr Cole Chemistry

Reactions of Aqueous Iron Ions

  • Questions
  • Answers
  1. For the following reactants, write the equation for the for the reaction and state what you would observe during the reaction.
    1. Iron(II) sulfate and sodium hydroxide.
    2. Iron(III) nitrate and sodium carbonate.
    3. Iron(III) sulfate and hydrochloric acid.
    4. Iron(II) sulfate and excess ammonia.
    5. Iron(II) sulfate and limited ammonia.
    6. Iron(III) hydroxide and acid.
    7. Iron(II) nitrate and sodium carbonate.
    8. Iron(II) hydroxide and acid.
    9. Iron(II) hydroxide and hydroxide.
    10. Iron(II) sulfate and hydrochloric acid.
    11. Iron(III) sulfate and sodium hydroxide.
    12. Iron(III) sulfate and limited ammonia.
    13. Iron(III) sulfate and excess ammonia.
    14. Iron(III) hydroxide and hydroxide.
  2. The following colour changes occurred. Suggest the equation for the reaction that occurred.
    1. Green solution –> yellow solution.
    2. Brown precipitate –> lilac solution.
    3. Green solution –> green precipitate (which then darkens in air).
    4. Green solution –> green precipitate (which does not darken in air).
    5. Orange solution –> yellow solution.
    6. Orange solution –> brown precipitate.
    7. orange solution –> brown precipitate & gentle bubbles.
  1. For the following reactants, write the equation for the for the reaction and state what you would observe during the reaction.
    1. Iron(II) sulfate and sodium hydroxide.
      [Fe(H2O)6]2+ + 2OH– –> Fe(H2O)4(OH)2 + 2H2O
      Green solution à green precipitate that darkens in the air
      Hydrolysis
    2. Iron(III) nitrate and sodium carbonate.
      2[Fe(H2O)6]3+ + 3CO32- –> 2Fe(H2O)3(OH)3 + 3H2O+ 3CO2
      orange solution –> brown precipitate & gentle bubbles
      Neutralisation
    3. Iron(III) sulfate and hydrochloric acid.
      [Fe(H2O)6]3+ + 4Cl– –> [FeCl4]– + 6H2O
      Pale violet or orange solution à yellow solution
      Ligand substitution reaction
    4. Iron(II) sulfate and excess ammonia.
      [Fe(H2O)6]2+ + 2NH3 –> Fe(H2O)4(OH)2 + 2NH4+
      Green solution to green precipitate
      Hydrolysis
    5. Iron(II) sulfate and limited ammonia.
      [Fe(H2O)6]2+ + 2NH3 –> Fe(H2O)4(OH)2 + 2NH4+
      Green solution to green precipitate
      Hydrolysis
    6. Iron(III) hydroxide and acid.
      Fe(H2O)3(OH)3 + 3H+ –> [Fe(H2O)6]3+
      Brown precipitate à violet solution or orange solution
      neutralisation
    7. Iron(II) nitrate and sodium carbonate.
      [Fe(H2O)6]2+ + CO32- –> FeCO3 + 6H2O
      Green solution à green precipitate
      Precipitation
    8. Iron(II) hydroxide and acid.
      Fe(H2O)4(OH)2 + 2H+ –> [Fe(H2O)6]2+
      Green precipitate à green solution
      Neutralisation
    9. Iron(II) hydroxide and hydroxide.
      No reaction
    10. Iron(II) sulfate and hydrochloric acid.
      [Fe(H2O)6]2+ + 4Cl– –> [FeCl4]2- + 6H2O
      Green solution à yellow solution
      Ligand exchange reaction
    11. Iron(III) sulfate and sodium hydroxide.
      [Fe(H2O)6]3+ + 3OH– –> Fe(H2O)3(OH)3 + 3H2O
      Lilac or orange solution à brown precipitate
      Hydrolysis reaction
    12. Iron(III) sulfate and limited ammonia.
      [Fe(H2O)6]3+ + NH3 –> Fe(H2O)3(OH)3 + 3NH4+
      Lilac or orange solution à brown precipitate
      Hydrolysis reaction
    13. Iron(III) sulfate and excess ammonia.
      [Fe(H2O)6]3+ + NH3 –> Fe(H2O)3(OH)3 + 3NH4+
      Lilac or orange solution à brown precipitate
      Hydrolysis reaction
    14. Iron(III) hydroxide and hydroxide.
      No reaction
  2. The following colour changes occurred. Suggest the equation for the reaction that occurred.
    1. Green solution –> yellow solution.
      [Fe(H2O)6]2+ + 4Cl– –> [FeCl4]– + 6H2O
    2. Brown precipitate –> lilac solution.
    3. Fe(H2O)3(OH)3 + 3H+ –> [Fe(H2O)6]2+
    4. Green solution –> green precipitate (which then darkens in air).
      [Fe(H2O)6]2+ + 2OH– –> Fe(H2O)4(OH)2 + 2H2O
      [Fe(H2O)6]2+ + 2NH3 –> Fe(H2O)4(OH)2 + 2NH4+
    5. Green solution –> green precipitate (which does not darken in air).
      [Fe(H2O)6]2+ + CO32- –> FeCO3 + 6H2O
    6. Orange solution –> yellow solution.
      [Fe(H2O)6]3+ + 4Cl– –> [FeCl4]– + 6H2O
    7. Orange solution –> brown precipitate.
    8. [Fe(H2O)6]3+ + 3OH– –> Fe(H2O)3(OH)3 + 3H2O
    9. orange solution –> brown precipitate & gentle bubbles.
      2[Fe(H2O)6]3+ + 3CO32- –> 2Fe(H2O)3(OH)3 + 3H2O+ 3CO2
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