Manganate (VII) redox titrations

• For redox titrations the procedures are very similar to acid-base titrations
• potassium manganate (VII) under acidic conditions
• In manganate titrations, MnO4- (aq) ions are reduced and so the other chemical must be a reducing agent that is oxidised
• Adding standard solution of potassium manganate (VII) to the burette


  1. Using a pipette, add a measured volume of the solution being analysed to the conical flask

  2. Add an excess of dilute sulfuric acid to provide the H+ ions required for the reduction of MnO4- ions

  3. Do not need to add an indicator - the reaction is self indicating
• Titration


  1. Manganate (VII) solution reacts and is decolourised as it is being added

  2. The end point of the titration is judged by the first permanent pink colour, indicating when there is an excess on MnO4- ions present

  3. This end point is one of the easiest to judge
• Repeat the titration until you get concordant titres (agree within +/- 0.10 cm3)
• Reading the meniscus - KMnO4- is a deep purple colour and it is very difficult to see the bottom of the meniscus through the intense colour. In manganate (VII) titrations, burette readings are read from the top rather than bottom of the meniscus - no difference bc the titre is the difference between 2 readings
• Examples of manganate (VII) titrations:

  • can be used for the analysis of many different reducing agents
  • iron (II) ions, Fe2+ (aq)
  • ethanedioic acid, (CHOOH)2 (aq)
  • same principles can be applied for redox titrations of other reducing reagents, provided that can reduce MnO4- to Mn2+
• The principles for redox titrations can be extended to the analysis of many different substances:

  • manganate (VII) titrations can be used to analyse reducing agents that reduce MnO4- to Mn2+
  • KMnO4- can be replaced with other oxidising agents, the commenest being acidified dichromate (VI), H+/Cr2O72-
  • the procedures and calculations are similar