23.2 - manganate (VII) redox titrations

• Two common redox titrations


  - Potassium manganate (VII) (KMnO₄ (aq)) under acidic conditions.

  - Sodium thiosulfate (Na₂S₂O₃ (aq)) for determination of iodine (I₂ (aq)).
• What is reduced and oxidised in manganate (VII) titrations?


  MnO₄⁻ (aq) ions are reduced and so the other chemical used must be a reducing agent that is oxidised.
• How do you read the meniscus in manganate (VII) titrations?


  From the top, rather than the bottom.
• Why do we read the meniscus from the top, rather than the bottom, in manganate (VII) titrations?


  As it is very difficult to see the bottom of the meniscus through the deep purple colour of potassium manganate (VII).