Redox Reactions Question 8
Question 8 - 2024 (30 Jan Shift 1)
$2 \mathrm{MnO}{4}^{-}+\mathrm{bI}^{-}+\mathrm{cH}{2} \mathrm{O} \rightarrow \mathrm{xI}{2}+\mathrm{yMnO}{2}+\mathrm{zOH}^{-}$
If the above equation is balanced with integer coefficients, the value of $z$ is ________.
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Answer (8)
Solution
$ \begin{aligned} \text { Reduction Half} & \quad {\text{Oxidation Half} } \ \left(2 \mathrm{MnO}{4}^{-} \rightarrow 2 \mathrm{MnO}{2} \right. & \left. \quad 2 \mathrm{I}^{-} \rightarrow \mathrm{I}_{2}+2 \mathrm{e}^{-}\right) \end{aligned} $
$ \begin{aligned} 2 \mathrm{MnO}{4}^{-}+4 \mathrm{H}{2} \mathrm{O}+6 \mathrm{e}^{-} \rightarrow 2 \mathrm{MnO}{2}+8 \mathrm{OH}^{-}-6 \mathrm{I}^{-} \rightarrow 3 \mathrm{I}{2}+6 \mathrm{e}^{-} \end{aligned} $
Adding oxidation half and reduction half, net reaction is
$2 \mathrm{MnO}{4}^{-}+6 \mathrm{I}^{-}+4 \mathrm{H}{2} \mathrm{O} \rightarrow 3 \mathrm{I}{2}+2 \mathrm{MnO}{2}+8 \mathrm{OH}^{-}$
$(\Rightarrow \mathbf{z}=8)$
$\Rightarrow$ Answer 8
