Question

Which of the following is/are correct regarding redox titrations?

• A. In titrations using potassium dichromate, $K_{2}C{r}_2{O}_7$ is used as a self-indicator.
• B. In titrations using potassium dichromate, external indicators like, diphenylamine are used.
• C. In titrations using potassium permangante, $KMn{O}_4$ is used as a self-indicator.
• D. In titrations using potassium permangante, external indicators like, diphenylamine are used.

Answer 1

Answer: (B), (C)

In titrations using potassium permangante, $KMn{O}_4$ is used as a self-indicator.

In the redox titrations using potassium permanganate, $KMn{O}_4$ serves as a self-indicator.
Potassium permanganate$\left(KMn{O}_4\right)$ is dark purple in nature. After the titration in acidic medium, it changes the color to pale pink due to the formation of $M{n}^{2+}$ at the end point. Since the function of the indicator is to detect end points, a separate indicator for permanganate titration is not needed. Thus $KMn{O}_4$ act as a self-indicator.

In redox titrations using potassium dichromate, external indicators like, diphenylamine, potassium ferricyanide etc. are used.