Difficulty: Easy
Correct Answer: all the above
Explanation:
Introduction / Context:
Polymers form via different mechanisms: addition (chain-growth) and condensation (step-growth). Understanding the difference is crucial in materials selection and processing. In condensation polymerization, functional groups react to form covalent bonds while eliminating small molecules as by-products, affecting processing (e.g., removal of water, HCl, or NH₃) and final properties.
Given Data / Assumptions:
Concept / Approach:
Condensation polymerization forms a high-molecular-weight product with simultaneous elimination of small molecules such as water, hydrogen chloride, methanol, or ammonia, depending on the reacting functional groups. For instance: nylon 6,6 (salt of adipic acid and hexamethylenediamine) eliminates water; reaction of acid chlorides with amines liberates HCl; certain aminoplast resins may release ammonia. Therefore, multiple types of small molecules can evolve during step-growth polymerization—hence “all the above.”
Step-by-Step Solution:
Verification / Alternative check:
Standard polymer chemistry texts categorize step-growth reactions with concomitant small-molecule elimination; industrial processes include venting or vacuum to remove by-products and push conversion.
Why Other Options Are Wrong:
Each of (a), (b), (c) is individually true in specific systems, but none alone is universally sufficient; the most complete statement is “all the above.”
Common Pitfalls:
Confusing condensation with addition polymerization (e.g., polyethylene) where no small molecule is eliminated; overlooking the need to remove by-products to reach high molecular weight.
Final Answer:
all the above
Discussion & Comments