More on transition elements

• What is the colour of aqueous Fe3+ and when OH- or NH3 is added, what is the colour change?

  Pale yellow and when OH- is added a pale yellow precipitate forms.
• What is the colour of aqueous Cr3+ and what is the colour change when OH- or NH3 is added?

  Violet colour and when OH- is added, a green precipitate forms
• What is the colour of aqueous Cu2+ and what is the colour change when OH- or NH3 is added?

  Blue colour and when OH- is added, a pale blue precipitate forms.
• What is the colour of aqueous Fe2+ and what is the colour change when OH- or NH3 is added?

  Pale green and when OH- is added, a green precipitate forms
• What is the colour of aqueous Mn2+ and what is the colour change when OH- or NH3 is added?

  Pale pink and when OH- is added, a pale brown precipitate forms
• When excess ammonia is added to Cr(OH)3, what is the colour change and what is formed?

  Green precipitate dissolves to form a deep purple solution and the complex ion [Cr(NH3)6]^3+ is formed
• What is the colour change when Cu(OH)2 reacts with excess ammonia?

  Pale blue precipitate dissolves to form a dark blue solution
• What is the complex ion formed when Cu(OH)2 reacts with excess ammonia?

  [Cu(NH3)4(H2O)2]^2+ + 2H2O + 2OH-
• What is the colour change and the products formed when 4Cl- ions are added to Cu^2+ (aq)?

  Blue to yellow colour change as [Cu(Cl)4]^2- and 6H2O.
• What happens if water is added to CuCl4 solution?

  Yellow to blue colour change as the water molecules will displace the chloride ions
• Why is CO considered toxic?

  Because CO is a better ligand than oxygen, so therefore bonds more strongly and irreversibly to iron in haemoglobin. This prevents oxygen from being transported to cells.
• What is a use of cis-platin and its action?

  It can be used to stop the replicating and dividing of cancerous cells. The chloride ions in cis platin are substituted by water molecules upon entry into the cell.The water molecules are removed to allow it to bind to the DNA, disrupting the structure of DNA.
• What are the side effects of using cis-platin in cancer treatment?

  It can affect healthy cells that replicate quickly, such as hair follicles.So hair loss is a side effect.
• Fe2+ can be oxidised to Fe3+ by MnO4-(potassium manganate can act as an oxidising agent).This happens in acidic conditions, hence H+ ions in the ionic equation.The colour change is from purple to colourless. This is because MnO4- is purple whereas Mn2+ is colourless.
• Fe3+ can be reduced to Fe2+ by the use of a reducing agent such as potassium iodide.The I- ions are oxidised to iodine. Fe3+ is orange-brown in colour.And the colour changes to pale green because of the presence of Fe2+ ions. However this is masked by the presence of iodine which is brown in colour.
• Dichromate ions can be reduced to Cr3+ ions by the use of zinc( a strong reducing agent). A colour change from orange to green occurs, since aqueous chromium is green.
• Cu2+ can be reduced to Cu+ by potassium iodide( a reducing agent). Iodide ions are oxidised to Iodine. CuI is formed which is a white precipitate.