Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A) : Wool has a soft handle, lower chemical resistance and good water and dye absorption.
Reason (R) : 70-75% of crystalline regions of the wool structure are responsible for the above properties.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Remember: High amorphous content = high moisture absorption, soft handle, and lower chemical resistance. Wool is highly amorphous, so any statement claiming it has "70-75% crystalline regions" must be false.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The physical and chemical properties of textile fibers (such as strength, flexibility, moisture absorbency, and chemical resistance) are determined by their internal polymer structure, specifically the ratio of crystalline (ordered) to amorphous (disordered) regions.

Step 2: Detailed Explanation:
Let us evaluate the Assertion and Reason individually:
- Assertion (A): "Wool has a soft handle, lower chemical resistance and good water and dye absorption."
This is scientifically true.
Wool is a natural protein fiber with a unique coiled polypeptide structure.
It is highly flexible, has a soft handle, absorbs moisture and dyes exceptionally well (due to its hydrophilic amino acid side chains), and is relatively sensitive to alkalis and chlorine bleaches.
- Reason (R): "70-75% of crystalline regions of the wool structure are responsible for the above properties."
This is scientifically false.
Wool is a highly amorphous fiber. It consists of approximately 60% to 70% amorphous regions and only 30% to 40% crystalline regions.
The high proportion of amorphous (disordered) regions allows water and dye molecules to enter the fiber structure easily, which is responsible for its high absorbency and lower chemical resistance.
If wool were 70-75% crystalline, it would be stiff, strong, and highly resistant to chemicals and moisture penetration (similar to nylon or polyester).
Since the Assertion is true and the Reason is false, the correct option is (C).

Step 3: Final Answer:
Assertion (A) is true, but Reason (R) is false.