JEE Advanced 2020 · Paper 2 · Chemistry Q3

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ChemistryInteger+3 / -1Question 21 of 54

In the chemical reaction between stoichiometric quantities of $\ce{KMnO4}$ and KI in weakly basic solution, what is the number of moles of $\ce{I2}$ released for 4 moles of $\ce{KMnO4}$ consumed?

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Answer and worked solution

Official answer: 6

In neutral or weakly basic solution permanganate is reduced only to $\ce{MnO2}$ (3 electrons):
$\ce{2MnO4- + 6I- + 4H2O -> 2MnO2 + 3I2 + 8OH-}.$
So 2 mol $\ce{KMnO4}$ give 3 mol $\ce{I2}$ , and 4 mol give 6 mol.

Answer: 6

Topics:Balancing redox reactions Important compounds (KMnO4, K2Cr2O7)

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