Interaction | Reaction | Process     Data Page

Pale green hexaaquairon(II) ion is oxidised by dense purple permanganate, or manganate(VII) ion, to mixture containing nearly colourless hydrated ions.

This reaction can be used in a self-indicating titration in which a dark purple aqueous solution of permanganate is added to a very, very pale green an iron(II) solution. The permanganate decolourises as it is stirred into the iron(II) solution, which is oxidised to iron(III). The end point is persisting pale purple (pink) colour, which comes from the excess permanganate. Protons are provided by dilute sulfuric acid, as there are redox problems with most other mineral acids.

Note the 5:1 mole ratio between Fe2+ and MnO4–.

5

[Fe(H2O)6]2+
  +  
[MnO4]–
  +  
4
H2SO4(aq)
  +  
2
H2O
         
5

[Fe(H2O)6]3+
  +  

[Mn(H2O)6]2+
  +  
4
[SO4]2–
Reactant Page Go To Go To
Hexaaquairon(II) ion     Reactions Using    Reactions Forming
Permanganate ion     Reactions Using    Reactions Forming
Sulfuric acid, aqueous     Reactions Using    Reactions Forming
Water     Reactions Using    Reactions Forming
Hexaaquairon(III) ion     Reactions Using    Reactions Forming
Hexaaquamanganese(II) ion     Reactions Using    Reactions Forming
Sulfate ion     Reactions Using    Reactions Forming

Interaction, Reaction, Process defined as:
British A-Level Chemistry: A2
Oxidation: Of Substrate By Reagent
Redox

© Mark R. Leach 1999 –

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