Question: why kmno4 is used as internal indicator?
Answer: When used as a titrant, as soon as the endpoint is reached and the KMnO4- is in excess, the solution has a permanent pink hue (provided that the solution is initially colorless). Thus KMnO4 acts as its own indicator. ... KMnO4 acts as a self indicator because of its deep violet color which is highly visible to naked eye.