redox titration

Question

KMnO4 acts as self-indicator because:

RankGuru · Accepted Answer

1. **Color Profile**: Potassium Permanganate ($KMnO_4$) is a deep **purple** solution due to the $MnO_4^-$ ion.
2. **Titration Event**: In a redox titration (acidic medium), $MnO_4^-$ is reduced to the $Mn^{2+}$ ion, which is virtually **colorless** (very faint pink).
3. **Endpoint Detection**: During titration, the added purple drop is immediately decolorized as it reacts with the reducing agent. 
4. **Mechanism**: Once the reducing agent is exhausted, the very next drop of $KMnO_4$ is not consumed. Its own purple color remains in the flask.
5. **Observation**: A permanent, **persistent faint pink color** marks the endpoint without needing an external indicator.

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redox titration

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