Test redox

• Potassium permanganate causes oxidation and is itself reduction
• Color change during the titration of potassium permanganate

  Purple to colorless
• Potassium permanganate is not a primary standard, so it is not possible to make up a solution of KMnO4 whose concentration is accurately known
• When making up a solution of ammonium iron (II) sulfate

  It MUST be dissolved in water containing dilute sulfuric acid to prevent oxidation by oxygen
• When KMnO4 is added to an acidified solution containing Fe+2 ions

  Fe+2 ions are oxidized, and Mn+2 ions are reduced
• Standardizing a solution of potassium permanganate

  By titration against a reducing agent which is a primary standard
• Potassium permanganate acts as its own indicator
• Method to work out the concentration of KMnO4

  Titrating against a solution containing Fe+2 ions
• Reasons for using Ammonium iron (II) Sulfate instead of iron sulfate

  • It can be obtained pure
  • It cannot be affected by air
  • Its formula is (NH4)2SO4. FeSO4.6H₂0
• Potassium permanganate

  • Has a very intense purple color and when reading the volume from a burette, the top of the meniscus is read instead of the bottom
  • Powerful oxidizing agent with intense color and low solubility, used in titrations at usually 0.02M solution
• End Points of the titration

  The first trace of permnant pink