Problem 70 - A Complete Resource Book in Chemistry for JEE Main

Question

Bleaching action of chlorine occurs in the presence of (a) moisture (b) sunlight (c) \(\mathrm{O}_{2}\) (d) dry air

Step-by-Step Solution

Answer

Chlorine's bleaching action occurs in the presence of moisture.

Step 1: Understanding the Question

We need to determine under which condition chlorine can effectively bleach substances. Specifically, we must identify the correct option among moisture, sunlight, \(\mathrm{O}_{2}\), or dry air.

Step 2: Chlorine's Bleaching Mechanism

Chlorine bleaches by a chemical reaction that involves the liberation of nascent (atomic) oxygen. This reaction requires moisture as water provides the medium to release nascent oxygen from chlorine.

Step 3: Eliminate Incorrect Options

- Sunlight is not needed for chlorine's bleaching action; it may actually decompose chlorine.- \(\mathrm{O}_{2}\) (molecular oxygen) is not the same as nascent oxygen and is not directly involved in the bleaching mechanism.- Dry air lacks the moisture necessary for the release of nascent oxygen.

Step 4: Conclusion

Given the process, moisture is crucial for the bleaching action of chlorine because it helps release nascent oxygen, which is the key to the bleaching effect. Thus, the correct answer is moisture.

Key Concepts

Chlorine Chemistry

Chlorine is a highly reactive element and plays a significant role in many chemical processes. It is a member of the halogen family and is often used for its bleaching and disinfecting properties.
When chlorine is added to water, it forms hypochlorous acid and hypochlorite ions, which are both effective bleaching agents. This chemical reaction is important because it lays the groundwork for understanding how chlorine acts in different environments.

• Chlorine can exist in different chemical forms depending on the conditions.
• It is used extensively in both industrial and household cleaning products.
• The bleaching properties of chlorine make it ideal for whitening clothes or disinfecting surfaces.

Understanding chlorine's chemistry is crucial for comprehending its interactions with other substances, particularly in its role as a bleaching agent.

Nascent Oxygen

Nascent oxygen refers to the highly reactive atomic form of oxygen. During the bleaching process, the nascent oxygen is generated from chlorine.
In chemical processes, nascent oxygen is often responsible for initiating or speeding up reactions due to its reactive nature.
For chlorine's bleaching action, nascent oxygen is responsible for breaking down the color-causing compounds in materials.

• Nascent oxygen is more reactive than the typical oxygen molecule, \(O_2\).
• It readily combines with other elements or compounds to cause oxidization.
• In the context of bleaching, the introduction of nascent oxygen is the main catalyst for color removal.

This explains why stronger bleaching is observed when the environment is suitable for the generation of nascent oxygen from chlorine.

Chemical Reactions in Moisture

Moisture is indispensable for the bleaching function of chlorine due to the chemical reactions it facilitates.
Water acts as a medium that enables chlorine to release nascent oxygen. This nascent oxygen is crucial because it performs the actual bleaching effect.
When chlorine comes into contact with moisture, it reacts to produce hydrochloric acid and nascent oxygen.

• Moisture breaks chlorine down into more reactive forms.
• The presence of water significantly enhances the bleaching effect.
• Without moisture, chlorine's potential to bleach effectively is drastically reduced.

In dry conditions, chlorine alone is not enough to achieve bleaching, underscoring the importance of moisture in chemical reactions involving chlorine.

Role of Water in Chemical Reactions

Water is not just a solvent but an active participant in many chemical reactions, including those needed for bleaching.
Its role is particularly prominent in reactions with chlorine where it aids in transforming these reactions through mechanisms like hydrolysis.
In the case of chlorine bleaching, water not only provides a medium for the chemical reactions but also participates actively by facilitating the release of nascent oxygen.

• Water acts as a catalyst in many chlorine-related chemical processes.
• The process of hydrolysis enabled by water is crucial for bleaching.
• It allows for the transformation of chlorine into more reactive species.

Water makes a substantial difference in how chlorine interacts with different substances, highlighting the fundamental role it plays in chloride chemistry and its applications.