Question

why KMnO4 act as a self indicator

Answer 1

Because potassium permanganate has a deep violet colour which is highly visible to the naked eye and when one titrates it and there is a loss of colour, it is apparent. So one does not need an indicator to tell you the end point.......

Answer 2

when we titrate Mohr's salt or any other with KMnO₄ the sol. becomes colorless after the titration is over when n extra drop of KMnO₄ is added to it the sol. becomes pinkish n indicates that the titration was over just one drop before.As here we dnt need any indicator to be indicated about the completion of the experiment and KMnO₄ itself acted as an indicator .