Problem 8 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

From the following statements regarding \(\mathrm{H}_{2} \mathrm{O}_{2}\), choose the incorrect statement : (a) It has to be stored in plastic or wax lined glass bottles in dark (b) It has to be kept away from dust (c) It can act only as an oxidizing agent (d) It decomposes on exposure to light

Step-by-Step Solution

Answer

Statement (c) is incorrect; \(H_2O_2\) can act as both an oxidizing and reducing agent.

Step 1: Understand the Properties of Hydrogen Peroxide

Hydrogen peroxide (\(H_2O_2\)) is a chemical compound that needs proper storage to maintain its stability. It is often stored in dark bottles to avoid decomposition because it easily breaks down in the presence of light. Dust can catalyze its decomposition into water and oxygen.

Step 2: Analyze Statement (a)

Statement (a) mentions that \(H_2O_2\) must be stored in plastic or wax-lined glass bottles in the dark. This is true because such storage prevents it from decomposing due to exposure to light.

Step 3: Evaluate Statement (b)

Statement (b) mentions that \(H_2O_2\) has to be kept away from dust. This is correct because dust can act as a catalyst in the decomposition of hydrogen peroxide, accelerating its breakdown.

Step 4: Examine Statement (c)

Statement (c) claims \(H_2O_2\) can act only as an oxidizing agent. This is incorrect. While \(H_2O_2\) is commonly known as an oxidizing agent, it can also act as a reducing agent under certain conditions.

Step 5: Consider Statement (d)

Statement (d) states that \(H_2O_2\) decomposes on exposure to light. This is true, as light can break down \(H_2O_2\) into water and oxygen.

Key Concepts

Storage Conditions

Hydrogen peroxide (\(H_2O_2\)) requires special storage conditions to maintain its stability. It is a highly reactive compound that decomposes easily. Therefore, it must be stored in a way that minimizes its exposure to the elements that trigger its breakdown.

• Dark Containers: \(H_2O_2\) is often stored in dark plastic or wax-lined glass bottles to protect it from light. Light exposure can accelerate its decomposition, resulting in water and oxygen.
• Temperature Control: Keeping hydrogen peroxide in a cool environment can help extend its shelf life. High temperatures can increase the rate of decomposition.
• Avoid Contamination: The storage area should be free from dust and impurities as these substances can catalyze its decomposition.

Proper storage helps in maintaining the efficacy of hydrogen peroxide for its intended use.

Oxidizing Agent

Hydrogen peroxide is widely recognized as a powerful oxidizing agent. An oxidizing agent is a substance that gains electrons in a chemical reaction. \(H_2O_2\) is capable of accepting electrons from other substances, thus facilitating their oxidation.

• Oxidizing Abilities: It can oxidize a variety of substances, including metals and organic compounds, making it useful in a range of applications, such as bleaching and disinfecting.
• Important Reactions: In reactions, it often gets reduced to water, donating oxygen to the substance it oxidizes.
• Usage in Industry: Its oxidizing property is leveraged in industries for creating a sterile environment and in the treatment of wastewater.

These properties are very important in both laboratory and industrial applications, providing a clean and efficient way to oxidize materials.

Reducing Agent

Interestingly, hydrogen peroxide can also serve as a reducing agent. A reducing agent donates electrons and reduces other substances. While more commonly an oxidizer, \(H_2O_2\) can act reductively under specific conditions.

• Dual Role: Depending on the reaction conditions, like pH and concentration, \(H_2O_2\) may donate electrons to other species.
• Applications: In such reactions, hydrogen peroxide can transform to make products that require a reduction step.
• Comparative Review: Its ability to act as both an oxidizing and reducing agent makes it versatile and valuable for diverse chemical processes.

This duality adds to the uniqueness and flexibility of hydrogen peroxide in various chemical reactions.

Decomposition

The decomposition of hydrogen peroxide is a fundamental property that significantly impacts its use and storage. \(H_2O_2\) tends to break down into water (\(H_2O\)) and oxygen (\(O_2\)) when exposed to certain conditions.

• Light-Induced Decomposition: Exposure to light is a key factor causing \(H_2O_2\) to decompose. This process releases oxygen gas, which is often observed as bubbles.
• Catalysts: Substances like dust and metal ions can accelerate the decomposition of hydrogen peroxide by acting as catalysts. This is why it is vital to store \(H_2O_2\) in a clean, contaminant-free environment.
• Reaction Overview: \(2H_2O_2 \rightarrow 2H_2O + O_2\) is the typical decomposition reaction. This simplicity is advantageous for oxygen generation on demand.

Understanding this property is essential for safely handling and utilizing hydrogen peroxide in both home and industrial settings.