JEE Advanced 2023 · Paper 2 · Chemistry Q8

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ChemistryInteger+4Question 42 of 51

$\ce{H2S}$ (5 moles) reacts completely with acidified aqueous potassium permanganate solution. In this reaction, the number of moles of water produced is $\mathbf x$ , and the number of moles of electrons involved is $\mathbf y$ . The value of $(\mathbf x + \mathbf y)$ is _____.

Your answer

Answer and worked solution

Official answer: 18

Balanced equation. In acid, $\ce{MnO4-}$ oxidises $\ce{H2S}$ to sulphur:
$\ce{5H2S + 2MnO4- + 6H+ -> 5S + 2Mn^2+ + 8H2O}.$

Counting.

Water: $\mathbf x=8$ mol.
Electrons: each S goes from $-2$ to 0, so $\mathbf y=5\times2=10$ mol.

$x+y=18.$

Topics:Balancing redox reactions Oxidation number

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