Acidified potassium permanganate acts as a strong oxidising agent and in doing so the purple manganate seven ion is reduced to
- A. the almost colourless manganese two ion
- B. manganese metal
- C. the green manganate six ion
- D. brown manganese dioxide
Explanation
In acidic solution permanganate is reduced from plus 7 to plus 2, and the sharp change from deep purple to almost colourless is what makes it self indicating in titrations. In neutral or alkaline conditions the reduction stops at manganese dioxide, giving a brown precipitate instead. The acid used must be dilute sulphuric acid, since hydrochloric acid would itself be oxidised to chlorine.
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