27. Which of the following is a thermosetting plastic?

A. PVC
B. Polyethylene
C. Nylon
D. Bakelite

28. What is the molecular formula of ethyl alcohol?

A. CH
B. C₂H₆O
C. CH₃OH
D. C₃H₇OH



Answer :

Final answer:

The answer explains the production, reaction type, monomers, and bond formation in Bakelite. It also discusses the melting points of PVC, polyethene, and polyester.


Explanation:

(a) The structural formula for Bakelite is a cross-linked polymer that can be represented as [-CH2-C6H4-CH2-]n. (b) The formation of Bakelite is a condensation reaction involving the elimination of a small molecule like water or alcohol. (c) The monomers for Bakelite belong to the group of phenols and aldehydes. The name of the monomers are phenol and formaldehyde. (d) A covalent bond forms between the monomers in the final polymer.

The key reason for the melting point difference: PVC has a higher melting point than polyethene due to its more ordered and tightly packed polymer structure, whereas polyester has an even higher melting point because of its highly polar and strong intermolecular forces like hydrogen bonding.


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