Some Basic Concepts of Chemistry - Result Question 1
1. An example of a disproportionation reaction is
(2019 Main, 12 April I)
(a) $2 \mathrm{MnO}_4^{-}+10 \mathrm{I}^{-}+16 \mathrm{H}^{+} \longrightarrow 2 \mathrm{Mn}^{2+}+5 \mathrm{I}_2+8 \mathrm{H}_2 \mathrm{O}$
(b) $2 \mathrm{NaBr}+\mathrm{Cl}_2 \longrightarrow 2 \mathrm{NaCl}+\mathrm{Br}_2$
(c) $2 \mathrm{KMnO}_4 \longrightarrow \mathrm{K}_2 \mathrm{MnO}_4+\mathrm{MnO}_2+\mathrm{O}_2$
(d) $2 \mathrm{CuBr} \longrightarrow \mathrm{CuBr}_2+\mathrm{Cu}$
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Answer:
Correct Answer: 1. (d)
Solution: In disproportionation reactions, same element undergoes oxidation as well as reduction.
Here, CuBr get oxidised to $\mathrm{CuBr}_2$ and also it get reduced to Cu . Other given reactions and their types are given below.
In the given reaction, $\mathrm{MnO}_4^{-}$get oxidised to $\mathrm{Mn}^{2+}$ and $\mathrm{I}^{-}$get reduced to $\mathrm{I}_2$. It is an example of redox reaction. The reaction takes place in acidic medium. $$ 2 \mathrm{KMnO}_4 \longrightarrow \mathrm{K}_2 \mathrm{MnO}_4+\mathrm{MnO}_2+\mathrm{O}_2 $$
The given reaction is an example of decomposition reaction. Here, one compound split into two or more simpler compounds, atleast one of which must be in elemental form. $$ 2 \mathrm{NaBr}+\mathrm{Cl}_2 \longrightarrow 2 \mathrm{NaCl}+\mathrm{Br}_2 $$
The given reaction is an example of displacement reaction. In this reaction, an atom (or ion) replaces the ion (or atom) of another element from a compound.
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