Question

Consider the change in oxidation state of Bromine corresponding to different emf values as shown in the diagram below : is Then the species undergoing disproportionation is

• A. $HBrO $
• B. $BrO^{-}_3$
• C. $ Br_2$
• D. $ BrO^{-}_4$

Answer 1

The Correct Option is A

To determine which species undergoes disproportionation, we need to understand what disproportionation involves. Disproportionation is a reaction in which a single substance is simultaneously oxidized and reduced, resulting in the formation of two different products.

In the provided options, we need to analyze the possible oxidation states for each species and see if any can disproportionate into two different oxidation states.

Let's consider the given species:

• HBrO: In this compound, Bromine is in the +1 oxidation state.
• BrO_3^−: Bromine is in the +5 oxidation state.
• Br_2: Bromine is in the 0 oxidation state.
• BrO_4^−: Bromine is in the +7 oxidation state.

To find the species which undergo disproportionation:

Disproportionation of HBrO:

The disproportionation reaction for HBrO is as follows:

2 HBrO \rightarrow HBr + HBrO_2

In this reaction:

• HBrO \rightarrow HBr: Bromine reduces from +1 to -1 oxidation state.
• HBrO \rightarrow HBrO_2: Bromine oxidizes from +1 to +3 oxidation state.

This satisfies the criteria for disproportionation since there is both oxidation and reduction happening to the same chemical species.

Other Options:

• BrO_3^− is already at a high oxidation state, more typically involved in reduction reactions.
• Br_2 can participate in redox reactions but does not disproportionate because it is already elemental bromine.
• BrO_4^− is at the highest oxidation state for bromine, tending to only undergo reduction.

Hence, the species undergoing disproportionation is HBrO.