23.2 Manganate (VII) redox titrations

• In a redox titration, a solution of a reducing agent is titrated with a solution of an oxidising agent
• Acidified manganate is an oxidising agent
• A standard solution of potassium manganate is added to the burette

  • Solution of the reducing agent is pipetted into the conical flask. Dilute sulfuric acid is added to supply H+ ions
  • Potassium manganate is added from the burette. It reacts with the reducing agent and its purple colour is decolourised
  • At the endpoint, the solution changes from colourless to permanent pink
• For other redox reactions, modifications may be needed depending on

  • oxidising agent used for the titration
  • reducing agent being analysed
  • the colour change
• Manganate titrations can be used to analyse an iron compound
• Reduction half equation for manganate:

  MnO4− ​+ 8H+ +5e− → Mn2+ + 4H2​O
• Oxidation half equation for iron:

  Fe2+ → Fe3+ + e−
• Overall iron manganate titration equation:

  MnO4−​ + 5Fe2+ + 8H+→Mn2+ + 5Fe3+ + 4H2​O