Transition and InnerTransition Elements - Result Question 9
9.
$ \begin{aligned} & \underline{A} \xrightarrow{4 \mathrm{KOH}, \mathrm{O}_2} \underset{\text { (Green) }}{2 \underline{B}}+2 \mathrm{H}_2 \mathrm{O} \\ & 3 \underline{B} \xrightarrow{4 \mathrm{HCl}} \underset{\text { (Purple) }}{2 \underline{\mathrm{C}}}+\mathrm{MnO}_2+2 \mathrm{H}_2 \mathrm{O} \\ & 2 \underline{C} \xrightarrow{\mathrm{H}_2 \mathrm{O}, \mathrm{KI}} 2 \underline{A}+2 \mathrm{KOH}+\underline{D} \end{aligned} $
(2019 Main, 11 Jan II)
In the above sequence of reactions, $\underline{A}$ and $\underline{D}$, respectively, are
(a) KI and $\mathrm{KMnO}_4$
(b) $\mathrm{MnO}_2$ and $\mathrm{KIO}_3$
(c) $\mathrm{KI}^2$ and $\mathrm{K}_2 \mathrm{MnO}_4$
(d) $\mathrm{KIO}_3$ and $\mathrm{MnO}_2$
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Answer:
Correct Answer: 9. (b)
Solution: When $\mathrm{MnO}_2(A)$ is fused with alkali in presence of air then potassium manganate $(B)$ is formed. Potassium manganate $(B)$ is of green colour which disproportionate in a neutral or acidic solution to produce potassium permanganate $(C)$. Potassium permanganate $(C)$ in presence of acidic medium oxidises iodide to iodate.
The reaction can be shown as:
Thus, $A$ and $D$ are $\mathrm{MnO}_2$ and $\mathrm{KIO}_3$ respectively.
BETA
