Intermediate Topic 680 of 1102 Inorganic Chemistry
Potassium Permanganate
A deep purple oxidant with Mn in +7 oxidation state used in titrations.
In-depth explanation of Potassium Permanganate
Potassium permanganate, KMnO4, is a dark purple salt in which manganese is in the +7 oxidation state, making it a powerful oxidizing agent. Its reduction product depends on pH: in strongly acidic solution it gives nearly colourless Mn2+, in neutral solution brown MnO2, and in strongly alkaline solution green manganate, MnO4 2-. Because the purple colour disappears on reduction, it acts as its own indicator in redox titrations. It is widely used to titrate iron(II), oxalate and hydrogen peroxide solutions. It is also used as a disinfectant.
Going deeper: Potassium Permanganate
Key ideas: KMnO4, purple. Made by fusing MnO2 with KOH and oxidant to K2MnO4 (green), then electrolytic oxidation or acid disproportionation. In acid, MnO4- + 8H+ + 5e- gives Mn2+ + 4H2O (E0 1.51 V), colorless endpoint, so it is self-indicator. In neutral or weakly alkaline, it forms MnO2 (brown), strongly alkaline gives MnO4 2-. Titration with Fe2+ and oxalate: 5Fe2+ per MnO4-, 5 oxalate per 2 MnO4-.
Common mistakes and connections: Students use HCl for acidification, which is oxidized to Cl2; use dilute H2SO4 only. Not a primary standard because it is impure and decomposes with light. Heating oxalate needed for rate at about 60 C. Mn(VII) is d0, so color comes from charge transfer. Links to redox titration, stoichiometry and transition metals oxidation states.
Visualization of Potassium Permanganate
Nernst plot for MnO4-/Mn2+ in acid (E0 1.51 V, five electrons): its high potential explains the strong oxidizing power of permanganate. The interactive lesson shows this as a live animation or chart.
Worked example and use case
In acid, purple MnO4- is decolourized as it oxidizes Fe2+: 5Fe2+ + MnO4- + 8H+ giving 5Fe3+ + Mn2+ + 4H2O.
Frequently asked questions about Potassium Permanganate
What is Potassium Permanganate?
A deep purple oxidant with Mn in +7 oxidation state used in titrations.
Is Potassium Permanganate a beginner, intermediate or advanced topic?
Potassium Permanganate is a intermediate topic in Inorganic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Potassium Permanganate?
Study these earlier topics in Inorganic Chemistry first: Copper Chemistry, Zinc Chemistry, Chromium Compounds.
What comes after Potassium Permanganate?
The next topics in Inorganic Chemistry are Silver Chemistry and Gold and Platinum.
Can I practise Potassium Permanganate with quizzes?
Yes. The interactive lesson includes a self-check question on Potassium Permanganate, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Potassium Permanganate fits in Inorganic Chemistry
Potassium Permanganate is topic 65 of 113 in Inorganic Chemistry.