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Question
The species given below that does NOT show a disproportionation reaction is ______.
Options
`"BrO"_2^-`
`"BrO"_4^-`
`"BrO"^-`
`"BrO"_3^-`
Solution
The species given below that does NOT show a disproportionation reaction is `underlinebb("BrO"_4^-)`.
Explanation:
A disproportionation reaction is a redox event in which the same species of one oxidation state undergoes simultaneous oxidation and reduction to produce two species with two distinct oxidation states. It is also known as a dismutation reaction.
The condition for disproportionation reaction is that the element should exhibit at least 3 different oxidation states and the element must be less stable in a particular oxidation state from which it can undergo both oxidation and reduction to produce species with a relatively stable oxidation state.
The oxidation states of Br in `"BrO"_2^-, "BrO"_4^-, "BrO"^- and "BrO"_3^-` are +4, +7, +1 and +5 respectively. The highest oxidation state of bromine is +7.
Of the aforementioned species, `"BrO"_4^-` does not experience disproportion since bromine is already present in this anion at the greatest oxidation of +7 and cannot be further oxidized.
All the remaining species will undergo disproportionation as they contain bromine in an oxidation state lower than that of +7 oxidation state.
Hence, the species that does not show a disproportionation reaction is `"BrO"_4^-`.
