Animated Solution for Chemistry - s and p-Block Elements: (A) $\text{HOCl}+{\text{H}}_2{\text{O}}_2⟶{\text{H}}_3{\text{O}}^{+}+{\text{Cl}}^{-}+{\text{O}}_2$ (B) ${\text{I}}_2+{\text{H}}_2{\text{O}}_2+2{\text{OH}}^{-}⟶2{\text{I}}^{-}+2{\text{H}}_2\text{O}+{\text{O}}_2$ Choose the correct option.

Hydrogen peroxide (${\text{H}}_2{\text{O}}_2$) is a fascinating molecule because it can act as both an oxidizing and a reducing agent depending on the chemical environment. In this problem, we are given two distinct chemical reactions and asked to determine the role of hydrogen peroxide in each.

Let's look at reaction (A):

To understand what is happening, we need to track the oxidation states of the key elements. Let's focus on chlorine. In hypochlorous acid ($\text{HOCl}$), oxygen has an oxidation state of $-2$ and hydrogen is $+1$. For the molecule to be neutral, chlorine must have an oxidation state of $+1$.

On the product side, we see the chloride ion (${\text{Cl}}^{-}$), which clearly has an oxidation state of $-1$. Since the oxidation state of chlorine decreases from $+1$ to $-1$, it is undergoing reduction.

Because $\text{HOCl}$ is being reduced, the substance causing this reduction must be the reducing agent. Therefore, ${\text{H}}_2{\text{O}}_2$ is acting as a reducing agent in this reaction. We can also verify this by looking at the oxygen in ${\text{H}}_2{\text{O}}_2$, which goes from an oxidation state of $-1$ to $0$ in ${\text{O}}_2$, meaning it is oxidized.

Now let's examine reaction (B):

Here, we focus on iodine. It starts as a neutral diatomic molecule (${\text{I}}_2$), so its oxidation state is $0$. On the product side, it becomes an iodide ion (${\text{I}}^{-}$), with an oxidation state of $-1$.

Just like in the first reaction, the oxidation state of iodine decreases from $0$ to $-1$, meaning it is being reduced. Consequently, ${\text{H}}_2{\text{O}}_2$ is once again acting as the reducing agent. Its own oxygen is oxidized from $-1$ to $0$, releasing oxygen gas.

In both equations (A) and (B), hydrogen peroxide reduces the other substance while getting oxidized itself. Therefore, it acts as a reducing agent in both reactions. This makes option (b) the correct choice.