practical 8

• Why should a metal be rubbed with emery paper before it is used as an electrode in a half-cell?

  To remove the thin layer of the metal oxide
• Outline a method to determine the standard electrode potential of an Fe2+/Fe3+ half-cell starting with solid samples of iron(II) sulfate, FeSO4 and iron(III) sulfate, Fe2(SO4)3. Include a diagram in your answer.

  > 1 mol dm-3 solution of iron(II) sulfate and 0.5 mol dm-3 iron(III) sulfate need to be produced

  > Make a standard solution (250 cm3) of iron(II) sulfate using 38.0 g of FeSO4

  > Make a standard solution (250 cm3) of iron(III) sulfate using 50.0 g Fe2(SO4)3

  > Set up the Fe2+/Fe3+ half-cell
• Outline a method to determine the standard electrode potential of an Fe2+/Fe3+ half-cell starting with solid samples of iron(II) sulfate, FeSO4 and iron(III) sulfate, Fe2(SO4)3. Include a diagram in your answer.

  > Connect the Fe2+/Fe3+ half-cell to the standard hydrogen electrode

  > Place a salt bridge between the two half-cells which is made using saturated potassium nitrate

  > Record the reading from the voltmeter = potential of the Fe2+/Fe3+