The chemical nature of hydrogen peroxide is
(a) oxidising and reducing agent in both acidic and basi

Q: Why is the oxidation state of oxygen in H2O2 -1 and not -2?

In $H_2O_2$, there is a direct single bond between the two oxygen atoms, known as a peroxide linkage ($H-O-O-H$). Because the two oxygen atoms share electrons equally between themselves, each oxygen only gains one electron effectively from its bonded hydrogen, resulting in an oxidation state of $-1$.

Q: Does H2O2 act as a stronger oxidising agent in an acidic or basic medium?

Hydrogen peroxide is generally a more powerful oxidising agent in an acidic medium. The presence of $H^+$ ions facilitates the reduction of $H_2O_2$ to $H_2O$, which is a highly favorable thermodynamic process.

Q: If it can do both, how do I know when it will act as an oxidising or reducing agent?

It depends entirely on the chemical it is reacting with. If it reacts with a strong oxidising agent (like $KMnO_4$ or $K_2Cr_2O_7$), $H_2O_2$ will be forced to act as a reducing agent. If it reacts with a reducing agent (like $Fe^{2+}$ or $I^-$), it will act as an oxidising agent.

Q: Why do we store hydrogen peroxide in dark bottles?

Because $H_2O_2$ can act as both an oxidising and reducing agent, it can react with itself (disproportionation) to form water and oxygen gas. This decomposition is catalyzed by light and trace metals, so it is stored in dark, wax-lined or plastic bottles to keep it stable.

Q: Can H2O2 reduce halogens?

Yes! For example, $H_2O_2$ can reduce halogens like Chlorine ($Cl_2$) to chloride ions ($Cl^-$) in a basic medium, while itself getting oxidised to oxygen gas ($O_2$).

Question

The chemical nature of hydrogen peroxide is

Options:

(A) oxidising and reducing agent in both acidic and basic medium

(B) oxidising and reducing agent in acidic medium, but not in basic medium

(C) reducing agent in basic medium, but not in acidic medium

(D) oxidising agent in acidic medium, but not in basic medium

Sigma Percentile · Accepted Answer

### The Chemical Chameleon: Hydrogen Peroxide

Hydrogen peroxide ($H_2O_2$) is one of the most fascinating molecules in inorganic chemistry. It acts like a chemical chameleon, adapting its behavior based on the substance it reacts with. To understand why it behaves this way, we need to look at the fundamental concept of oxidation states.

### The Secret Lies in the Oxidation State

In a molecule of water ($H_2O$), oxygen has an oxidation state of $-2$. In elemental oxygen gas ($O_2$), its oxidation state is $0$. However, in hydrogen peroxide ($H_2O_2$), oxygen exists in a unique **peroxide linkage** ($-O-O-$), which gives it an intermediate oxidation state of **$-1$**.

Because $-1$ is exactly halfway between its common minimum ($-2$) and maximum ($0$) oxidation states, hydrogen peroxide has a choice. It can either gain electrons to reach $-2$ (acting as an oxidizing agent) or lose electrons to reach $0$ (acting as a reducing agent). This dual capability is what makes $H_2O_2$ so versatile.

### Acting as an Oxidising Agent

When $H_2O_2$ acts as an oxidizing agent, it forces another substance to lose electrons while it gets reduced itself. This happens seamlessly in both acidic and basic environments:

**In Acidic Medium:**
$$H_2O_2 + 2H^+ + 2e^- \rightarrow 2H_2O$$
Here, the oxygen atom goes from an oxidation state of $-1$ to $-2$ in water.

**In Basic Medium:**
$$H_2O_2 + 2e^- \rightarrow 2OH^-$$
Again, the oxygen atom is reduced from $-1$ to $-2$ in the hydroxide ion.

### Acting as a Reducing Agent

Conversely, when $H_2O_2$ encounters a stronger oxidizing agent (like $KMnO_4$), it acts as a reducing agent. It donates electrons and gets oxidized to oxygen gas ($O_2$). This also occurs in both mediums:

**In Acidic Medium:**
$$H_2O_2 \rightarrow O_2 + 2H^+ + 2e^-$$
The oxygen atom's oxidation state increases from $-1$ to $0$.

**In Basic Medium:**
$$H_2O_2 + 2OH^- \rightarrow O_2 + 2H_2O + 2e^-$$
Once again, oxygen is oxidized from $-1$ to $0$.

### The Final Verdict

Because hydrogen peroxide can effortlessly slide up or down the oxidation state ladder regardless of the pH of the solution, it acts as **both an oxidising and reducing agent in both acidic and basic mediums**.

**Bonus Insight:** This dual nature also means $H_2O_2$ can react with itself! One molecule oxidizes another in a process called **disproportionation** ($2H_2O_2 \rightarrow 2H_2O + O_2$). This is precisely why hydrogen peroxide is stored in dark, wax-lined bottles—to prevent light from accelerating this self-destruction!

Animated Solution for Chemistry - s and p-Block Elements: The chemical nature of hydrogen peroxide is

Select Answer:

Visualized Solution

H_2O_2 \text{ Oxidation State}

\text{Intermediate Oxidation State}

\text{As an Oxidising Agent}

\text{As a Reducing Agent}

\text{Conclusion}

\text{Disproportionation}

The Sigma Insight: Hydrogen, Hydrides and Water

The Chemical Chameleon

The Secret Lies in the Oxidation State

Acting as an Oxidising Agent

Acting as a Reducing Agent

The Final Verdict

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