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A solution of KMnO4 on reduction yields either

Question:

A solution of KMnO4 on reduction yields either colourless solution or a brown precipitate or a green solution depending on the pH of the solution. What different stages of the reduction do these represent and how are they carried out?

Solution:

In acidic medium, permanganate changes to manganous ion which is colourless.

MnO4-+8H+ + 5e-→ Mn2+ + 4H2O

(colourless)

In alkaline medium, permanganate changes to manganate, which is a green solution

MnO4-+ e- → MnO42-

(green)

In a neutral medium, permanganate changes to manganese dioxide which is a brown precipitate,

MnO4-+ 2H2O + 3e-→ MnO2 + 4OH-

(brown)

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