Problem 88 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following statements is correct about polymers? (1) polymers are substances made up of recurring structural units, each of which can be regarded as derived from a specific compound called a monomer (2) polymers made from a single monomeric species are called homopolymers, whereas, those made up of two or more different monomeric species are called copolymers. (3) very often, polymers are macromolecules, and a sample of a given polymer is characteristically a mixture of molecules with different molecular weights (a) 1 and 2 only (b) 1 and 3 only (c) 1,2 and 3 (d) 2 only

Step-by-Step Solution

Answer

(c) 1, 2, and 3

Step 1: Understand the Concept of Polymers

Polymers are large molecules composed of repeating structural units, typically connected by covalent chemical bonds. The repeating units are derived from either one type of monomer or multiple monomer types.

Step 2: Analyzing Statement 1

Statement 1 states that polymers are substances made up of recurring structural units derived from a specific compound called a monomer. This description aligns with the definition of polymers as they are made from monomers linked together, so this statement is correct.

Step 3: Analyzing Statement 2

Statement 2 discusses two types of polymers: homopolymers and copolymers. Homopolymers are made from a single type of monomer, while copolymers consist of two or more different monomer species. This statement is correct as it accurately describes these classifications of polymers.

Step 4: Analyzing Statement 3

Statement 3 claims that polymers are often macromolecules, and samples are characteristically a mixture of molecules with different molecular weights. This is true as polymerization processes typically produce a range of molecular weights, and polymers are generally large molecules, making this statement correct too.

Step 5: Combining Verified Statements to Determine the Correct Answer

Since we have verified that all three statements (1, 2, and 3) are correct, the correct answer to the question is option (c) 1, 2, and 3.

Key Concepts

Monomers

Monomers are the building blocks of polymers. These small molecules can join together through chemical bonds to form the long chains that characterize polymers. Each monomer has a specific, simple chemical structure, usually involving a few atoms, which makes them versatile for constructing larger molecules. For example, ethylene, a simple monomer, polymerizes to form polyethylene, a common plastic.

• Monomers themselves are typically simple and reactive, allowing them to form stable links with similar units.
• By undergoing polymerization, monomers become part of the larger, more complex polymer structure.

Understanding monomers is essential because their chemical nature defines the physical and chemical properties of the polymers they create. When monomers combine, they can do so in many configurations, leading to a diverse range of polymers for myriad applications in everyday life, including textiles, packaging, and medical devices.

Homopolymers

Homopolymers are polymers in which all the repeating structural units are the same. These polymers are derived from a single type of monomer, which makes the entire polymer chain uniform. This uniformity often results in predictable properties, which can be a significant advantage in manufacturing and application.

• Common examples include polyethylene and polystyrene, both produced from a singular monomer.
• Homopolymers tend to have consistency in terms of strength, flexibility, and other physical properties, which is useful in applications where uniformity is key, such as in food packaging or producing plastic containers.

The production and use of homopolymers are crucial in industries that require reliable performance without variation. However, their simplicity can also be a limitation when diverse material properties are needed.

Copolymers

Copolymers are polymers made from two or more different monomers. This combination allows for the customization of the polymer's properties by incorporating attributes from each monomeric species. By varying the type, sequence, and proportion of the monomers, manufacturers can create a wide range of materials suited for specific purposes.

• Copolymers can be designed with alternating, random, block, or graft arrangements of the monomers, each offering unique structural properties.
• An example is styrene-butadiene rubber (SBR), used in car tires, which combines the characteristics of both of its monomers to enhance performance.

The diversity offered by copolymers makes them invaluable in fields like automotive, aerospace, and textiles, where specific material properties such as durability, elasticity, and resistance to various environmental factors are needed. Therefore, the flexible nature of copolymers' structural configuration presents significant creative opportunities for material scientists.