Which of the following oxidizing reagents is used as a selfindicator ?

Options

A. ` KMnO_4`
B. `K_2Cr_2O_7`
C. `CuSO_4`
D. both (1) and (2)

Answer

A

Explanation

`MnO_4^(-)` acts as the self indicator . The visible endpoint in this case is achieved after the last of the reductant `(Fe^(2+)" or "C_2O_4^(2-))` is oxidized . The first lasting tinge of pink color appears at `MnO_4^(-)` concentration as low as ` 10^(-6) ml L^(-1)`. This ensures a minimal overshoot in color beyond the equivalence point - the point where the reductant and the oxidant are equal in terms of their mole stoichiometry . In `KMnO_4` , the color change is so sensitive that it can be detected easily even at very low concentrations which is not the case with `K_2Cr_2O_7`. Therefore , unlike `KMnO_4, K_(2)Cr_2O_7` is not a self indicator .