Mr Cole Chemistry

Mixed Reactions of Aqueous Ions Questions

  • Questions
  • Answers
  1. For the following reactions, write the ionic equation for the reaction; state the colour change and state the type of reaction occurring.
    1. Ammonia solution added to iron(II) sulfate dropwise with a pipette.
    2. A large quantity of concentrated ammonia added to copper(II) sulfate.
    3. Copper sulfate and sodium chloride mixed together in a test tube.
    4. Sodium carbonate solution added to a solution of iron(III) nitrate dropwise.
    5. Excess concentrated ammonia added to a solution of iron(II) sulfate.
    6. Hydrochloric acid added to iron(II) hydroxide in a test tube.
    7. Solid iron(II) hydroxide added to a solution of sodium hydroxide.
    8. Dilute ammonia added dropwise to iron(III) sulfate.
    9. Nitric acid added to copper(II) hydroxide in a test tube.
    10. A large quantity of concentrated ammonia added to a solution of iron(III) sulfate.
    11. Sodium hydroxide added dropwise to iron(III) hydroxide.
    12. Limited quantity of sodium hydroxide added to a solution of aluminium nitrate.
    13. Concentrated hydrochloric acid added to solution of aluminium sulfate.
    14. Ammonia solution added to aluminium nitrate.
    15. Dilute ammonia added dropwise to a solution of copper(II) ions.
    16. Solid sodium carbonate added slowly to a solution of aluminium sulfate.
    17. Sulfuric acid added dropwise onto aluminium hydroxide.
    18. Nitric acid added to iron(III) hydroxide
    19. Sodium carbonate solution added to a solution of iron(II) nitrate.
  2. For the following colour changes, write the ionic equation for the possible reactions that could have caused that colour change.
    1. Green solution becomes a yellow solution on the addition of a colourless solution.
    2. Blue solution forms a blue precipitate on the addition of a colourless solution.
    3. A green solution becomes a green precipitate on the addition of a colourless solution.
    4. A blue solution becomes a blue-green precipitate on the addition of a white solid.
    5. Colourless solution forms a white precipitate on addition of a colourless solution.
    6. Orange solution forms a brown precipitate on addition of a colourless solution.
    7. A white precipitate dissolves to form a colourless solution on addition of a colourless solution.
    8. A lilac solution turns yellow on the addition of a colourless solution.
  3. Fe(II) sulfate and Fe(III) sulfate undergo different reactions with sodium carbonate solution.
    1. Write the ionic equation for the two reactions.
    2. Explain why they undergo different reactions.
  1. For the following reactions, write the ionic equation for the reaction; state the colour change and state the type of reaction occurring.
    1. Ammonia solution added to iron(II) sulfate dropwise with a pipette.
      [Fe(H2O)6]2+ + 2NH3 –> Fe(H2O)4(OH)2 + 2NH4+
      Green solution to green precipitate
      Hydrolysis
    2. A large quantity of concentrated ammonia added to copper(II) sulfate.
      [Cu(H2O)6]2+ + 4NH3 –> [Cu(NH3)4(H2O)2]2+ + 4H2O
      The blue solution becomes a dark blue solution.
      Ligand substitution reaction.
    3. Copper sulfate and sodium chloride mixed together in a test tube.
      [Cu(H2O)6]2+ + 2OH– –> Cu(H2O)4(OH)2 + 2H2O
      The blue solution forms a blue precipitate.
      Hydrolysis.
    4. Sodium carbonate solution added to a solution of iron(III) nitrate dropwise.
      2[Fe(H2O)6]3+ + 3CO32- –> 2Fe(H2O)3(OH)3 + 3H2O+ 3CO2
      Orange solution (or lilac) forms a brown precipitate. Bubbles.
      Neutralisation reaction / hydrolysis.
    5. Excess concentrated ammonia added to a solution of iron(II) sulfate.
      [Fe(H2O)6]2+ + 2NH3 –> Fe(H2O)4(OH)2 + 2NH4+
      The green solution forms a green precipitate.
      Hydrolysis.
    6. Hydrochloric acid added to iron(II) hydroxide in a test tube.
      Fe(H2O)4(OH)2 + 2H+ + 4Cl– –> [FeCl4]2- + 6H2O
      Green solid dissolves forming a yellow solution.
      Neutralisation reaction followed by a ligand substitution reaction.
    7. Solid iron(II) hydroxide added to a solution of sodium hydroxide.
      No reaction occurs – the solid green precipitate remains solid green.
    8. Dilute ammonia added dropwise to iron(III) sulfate.
      [Fe(H2O)6]3+ + 3NH3 –> Fe(H2O)3(OH)3 + 3NH4+
      Lilac (or orange) solution forms a brown precipitate.
      Hydrolysis
    9. Nitric acid added to copper(II) hydroxide in a test tube.
      Cu(H2O)4(OH)2 + 2H+ –> [Cu(H2O)6]2+
      The blue precipitate dissolves to form a blue solution.
      Neutralisation.
    10. A large quantity of concentrated ammonia added to a solution of iron(III) sulfate.
      [Fe(H2O)6]2+ + 2NH3 –> Fe(H2O)4(OH)2 + 2NH4+
      The green solution forms a green precipitate
      Hydrolysis.
    11. Sodium hydroxide added dropwise to iron(III) hydroxide.
      [Fe(H2O)6]3+ + 3OH– –> Fe(H2O)3(OH)3 + 3H2O
      The lilac or orange solution forms a brown precipitate
      Hydrolysis.
    12. Limited quantity of sodium hydroxide added to a solution of aluminium nitrate.
      [Al(H2O)6]3+ + 3OH– –> Al(H2O)3(OH)3 + 3H2O
      The colourless solution forms a white precipitate
      Hydrolysis.
    13. Concentrated hydrochloric acid added to solution of aluminium sulfate.
      [Al(H2O)6]3+ + 4Cl– –> [AlCl4]– + 6H2O
      The colourless solution remains a colourless solution.
      Ligand Substitution.
    14. Ammonia solution added to aluminium nitrate.
      [Al(H2O)6]3+ + 3NH3 –> Al(H2O)3(OH)3 + 3 NH4+
      The colourless solution forms a white precipitate.
      Hydrolysis.
    15. Dilute ammonia added dropwise to a solution of copper(II) ions.
      [Cu(H2O)6]2+ + 2NH3 –> Cu(H2O)4(OH)2 + 2NH4+
      The blue solution precipitates to form a blue precipitate.
      Hydrolysis.
    16. Solid sodium carbonate added slowly to a solution of aluminium sulfate.
      2[Al(H2O)6]3+ + 3CO32- –> 2Al(H2O)3(OH)3+ 3H2O + 3CO2
      The colourless solution forms a white precipitate. Bubbles given off.
      Neutralisation.
    17. Sulfuric acid added dropwise onto aluminium hydroxide.
      Al(H2O)3(OH)3 + 3H+ –> [Al(H2O)6]3+
      The white precipitate dissolves to form a colourless solution.
      Neutralisation.
    18. Nitric acid added to iron(III) hydroxide
      Fe(H2O)3(OH)3 + 3H+ –> [Fe(H2O)6]3+
      The brown precipitate dissolves forming a lilac or orange solution.
      Neutralisation reaction.
    19. Sodium carbonate solution added to a solution of iron(II) nitrate.
      [Fe(H2O)6]2+ + CO32- –> FeCO3 + 6H2O
      A green solution forms green precipitate
      Precipitation
  2. For the following colour changes, write the ionic equation for the possible reactions that could have caused that colour change.
    1. Green solution becomes a yellow solution on the addition of a colourless solution.
      Fe(H2O)6 + 4Cl– –> [FeCl4]2- + 6H2O
    2. Blue solution forms a blue precipitate on the addition of a colourless solution.
      [Cu(H2O)6]2+ + 3OH– –> Cu(H2O)3(OH)3 + 3H2O
      [Cu(H2O)6]2+ + 3NH3 –> Cu(H2O)3(OH)3 + NH4+
    3. A green solution becomes a green precipitate on the addition of a colourless solution.
      [Fe(H2O)6]2+ + 3OH– –> Fe(H2O)3(OH)3 + 3H2O
      [Fe(H2O)6]2+ + 3NH3 –> Fe(H2O)3(OH)3 + NH4+
      [Fe(H2O)6]2+ + CO32- –> FeCO3 + 6H2O
    4. A blue solution becomes a blue-green precipitate on the addition of a white solid.
      [Cu(H2O)6]2+ + NaCO3 –> CuCO3 + 6H2O+ Na+
      (Note the solid NaCO3 cannot be split up into its ions)
    5. Colourless solution forms a white precipitate on addition of a colourless solution.
      [Al(H2O)6]3+ + 3OH– –> Al(H2O)3(OH)3 + 3H2O
      [Al(H2O)6]3+ + 3NH3 –> Al(H2O)3(OH)3 + 3 NH4+
    6. Orange solution forms a brown precipitate on addition of a colourless solution.
      [Fe(H2O)6]3+ + 3OH– –> Fe(H2O)3(OH)3 + 3H2O
      [Fe(H2O)6]3+ + NH3 –> Fe(H2O)3(OH)3 + 3NH4+
    7. A white precipitate dissolves to form a colourless solution on addition of a colourless solution.
      Al(H2O)3(OH)3 + OH– –> [Al(H2O)2(OH)4]– + H2O
      Al(H2O)3(OH)3 + 3H+ –> [Al(H2O)6]3+
    8. A lilac solution turns yellow on the addition of a colourless solution.
      [Fe(H2O)6]3+ + 4Cl– –> [FeCl4]– + 6H2O
  3. Fe(II) sulfate and Fe(III) sulfate undergo different reactions with sodium carbonate solution.
    1. Write the ionic equation for the two reactions.
      2[Fe(H2O)6]3+ + 3CO32- –> 2Fe(H2O)3(OH)3 + 3H2O+ 3CO2
      [Fe(H2O)6]2+ + CO32- –> FeCO3 + 6H2O
    2. Explain why they undergo different reactions.
      Fe3+ ions are more polarising than Fe2+ ions.
      This means that it is easier for the O-H bond in the water ligands to break in the Fe3+ complex that in the Fe2+ complex.
      This results in the following reaction: [Fe(H2O)6]3+ + H2O ⇌ [Fe(H2O)5OH]2+ + H3O+
      The H3O+ ions react with the carbonate ions.
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