Question

Which one of the following act as a self-indicators ?

• A. Potassium permanganate
• B. Potassium dichromate
• C. Phenolphthlein
• D. (a) and (b) above.

Answer 1

The correct option is A Potassium permanganate

Potassium permanganate$\left(KMn{O}_4\right)$ act as a self-indicator.
When Potassium permanganate$KMn{O}_4$ used as a titrant against solutions like oxalic acid and ferrous ammonium sulphate. $KMn{O}_4$ oxidises these standard solutions.
as soon as the end point is reached and the $KMn{O}_4$ is in excess, the solution has a permanent pale pink sas there is no more standard solution left to oxidise.
Thus $KMn{O}_4$ act as a self- indicator.