Geo-Scientist Prelims 2024 Chemistry Q39: While performing the titration of KMnO₄ with clear Mohr's salt…

While performing the titration of KMnO₄ with clear Mohr's salt solution, a student obtained brown precipitate in the conical flask instead of a colourless solution, much before the end point was reached. What could be the possible source of error?

1. (a) Reaction mixture was not heated to 60 °C
2. (b) Fe²⁺ in the Mohr's salt solution hydrolyzed to precipitate brown hydroxide
3. (c) Reaction medium was not made acidic
4. (d) Too large quantity of KMnO₄ had been added to the Mohr's salt solution