Problem 49 - Arihant Objective Approach to Organic Chemistry for IIT JEE and NEET all Medical Entrances Part 4

Question

Ebonite is : (a) synthetic rubber (b) natural rubber (c) polypropene (d) highly vulcanised rubber

Step-by-Step Solution

Answer

Ebonite is highly vulcanised rubber (d).

Step 1: Understand the Material

Ebonite is a type of hardened rubber. It is typically used to make hard rubber products, which are durable and resistant to impact.

Step 2: Define Vulcanisation

Vulcanisation is a chemical process for converting natural rubber or related polymers into more durable materials. This process usually involves adding sulfur or other equivalent curatives or accelerators to the rubber.

Step 3: Identify Ebonite Characteristics

Ebonite is created by vulcanising natural rubber for an extended period, leading to a material that is hard, black, and often shiny. This process involves a significantly higher amount of sulfur compared to normal vulcanisation.

Step 4: Match Options

Given the characteristics of ebonite—being a durable, shinier, and harder material due to extended vulcanisation—it aligns with option (d) "highly vulcanised rubber."

Key Concepts

Ebonite: A Special Type of Rubber

Ebonite is a form of rubber that has undergone extensive vulcanisation. It is uniquely characterized by its toughness and resilience. This material is often recognized for its distinctive black color and high gloss finish.
Unlike the elastic nature of typical rubber, ebonite is hard and rigid, making it suitable for products like bowling balls, electrical insulators, and musical instruments. Ebonite's increased resistance to wear and impact is a result of its highly vulcanised structure. This process effectively transforms the flexible, stretchy natural rubber into something much more durable and long-lasting. By understanding ebonite's unique properties, we can appreciate its invaluable role in producing hard rubber goods.

Understanding Natural Rubber

Natural rubber is a flexible, stretchy polymer harvested from the latex sap of rubber trees. It is made up of long chains of isoprene units, which give it its elasticity and strength. Natural rubber is known for its:

• High elasticity
• Good abrasion resistance
• Excellent tensile strength

These properties make it incredibly useful in many applications, including tires, footwear, and industrial products.
However, natural rubber in its raw form can be soft and sticky, which limits its usefulness in certain applications. The vulcanisation process, which includes adding sulfur, enhances natural rubber's properties, turning it into more durable forms like ebonite. This transformation allows rubber to maintain its useful properties while also becoming more versatile and suitable for a broader range of applications.

The Role of Sulfur in Vulcanisation

Sulfur plays a crucial role in the vulcanisation process, which is essential for converting natural rubber into more durable forms.
This process involves heating rubber with sulfur, which creates cross-links between the polymer chains within the rubber. These cross-links dramatically alter the properties of rubber by enhancing:

• Strength
• Elasticity
• Weather resistance

In the case of ebonite, a substantial amount of sulfur is used, resulting in a highly cross-linked, hard rubber substance. This solves the problem of rubber's inherent stickiness and brittleness, making it more versatile for various industrial applications. Understanding the importance of sulfur in vulcanisation helps us grasp how materials like ebonite are developed and why they exhibit their particular characteristics.

The Wonders of Polymer Chemistry

Polymer chemistry is the science of large, repetitive molecules known as polymers. Rubber is a naturally occurring polymer composed predominantly of the molecule isoprene.
Vulcanisation, which involves altering these polymer chains, showcases polymer chemistry in action. By adding chemicals like sulfur, we can create new substances with enhanced properties.
Understanding polymer chemistry gives us insights into the creation of everyday and specialized materials, including:

• Rubber tires
• Plastics
• Synthetic fibers

Through polymer chemistry, we learn to manipulate natural substances like rubber, making them more useful in various industries. It enables the development of innovative materials like ebonite, highlighting the pivotal role of chemistry in technological advancements and material science.