Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Teaching & Learning Packages The Nernst Equation and Pourbaix Diagrams Example 3
The Nernst Equation and Pourbaix Diagrams AimsBefore you startIntroductionBackgroundThe Nernst equationConstruction of a Pourbaix DiagramAnatomy of a Pourbaix DiagramExamples of a Pourbaix DiagramConstructing a 3D Pourbaix DiagramSummaryQuestionsGoing further
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Example 3

Find the electrochemical reaction for an equilibrium between MnO4- and MnO2

1. Write reduced species on right

 MnO4-  →  MnO2

2. Balance Mn atoms

 MnO4-  →  MnO2

3. Balance oxygen atoms with water

 MnO4-  →  MnO2 + 2H2O

4. Balance hydrogen atoms with hydrogen ions

 MnO4-  + 4 H+ →  MnO2 + 2H2O

5. Balance charge with electrons

 MnO4-  + 4 H+ + 3 e- →  MnO2 + 2H2O

Check: Each side of the equation has: One Mn, four O, four H and zero residual charge – so it is balanced.

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