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NEET levelSingle correct optionDifficulty 1 of 3eq185

No external indicator is needed in the titration of $Fe X^{2 +}$ against acidified $KMnO X_{4}$ because:

A $KMnO X_{4}$ is intensely coloured, so the first slight excess gives a permanent pink colour
Bthe pH of the solution changes sharply at the equivalence point
C $Fe X^{3 +}$ formed is colourless and turns pink at the equivalence point
D $Mn X^{2 +}$ formed gives a deep blue colour at the equivalence point

Answer: A

Permanganate is deep purple while its reduction product

Mn X^{2 +}

is almost colourless. At the equivalence point the first excess drop of

KMnO X_{4}

imparts a persistent pink colour, so it is a self-indicator.

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