This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Classification of Polymers”.
1. Which of the following is a co-polymer?
Explanation: A polymer formed from on type of monomer is called a homopolymer. Polythene, PVC and PAN are homopolymers. A polymer formed from two or more different monomers is a co-polymer or a mixed polymer.
2. Polymers are not classified on the basis of which of the following?
b) Number of monomers
c) Method of preparation
Explanation: Polymers are very large molecules formed by joining together huge number of simple units, or monomers. They are mainly classified on the basis of their source, structure, mode of synthesis and molecular forces.
3. Which of the following types of polymers is not based on the classification by the source?
Explanation: On the basis of source, polymers are classified as natural, semi-synthetic or synthetic. Elastomers are a class of polymers based on the molecular forces.
4. Which of the following is not a natural polymer?
Explanation: The polymers obtained from plants and animals are called natural polymers. Rayon is a semi-synthetic polymer which is derived from a natural polymer by chemical modification. Cellulose on acetylation with acetic anhydride in sulphuric acid gives cellulose acetate polymer or rayon.
Explanation: The shown structure has unconnected linear chains with some intermediate branches. This is a branched chain polymer. They are irregularly packed and have lower density and strength than linear polymers.
6. All macromolecules are polymers.
Explanation: Polymers consists of thousands of repeating units, and are macromolecules because of their very large size and high molecular mass (103 to 107 u). However, a macromolecule may or may not contain repeating monomer units (for example, chlorophyll). Therefore, all polymers are macromolecules, but all macromolecules are not polymers.
7. The synthesis of which of the following polymers involves the repeated loss of small molecules?
Explanation: Condensation polymers are formed by the repeated condensation reaction between two different bi-functional or tr-functional monomeric units, along with the loss of small molecules like water, alcohol, HCl, etc. Nylon-6,6 is formed by the condensation of hexamethylene diamine and adipic acid, resulting in loss of water molecules.
8. The compound [-CH2-CH(C6H5)–]n is a ________
c) condensation polymer
d) network polymer
Explanation: [-CH2-CH(C6H5)–]n is a homopolymer with a linear structure. It is obtained from the addition polymerisation of the monomer styrene, C6H5CH=CH2.
9. Which of the following is not an elastomer?
Explanation: Elastomers are polymers that have rubber like elastic properties. The polymer chains are held together by the weakest intermolecular forces, which facilitate the stretching of the polymer. PVC is a plastic and not an elastomer.
10. Which of the following fibres does not have dipole-dipole interactions?
Explanation: Fibres are polymers which have strong intermolecular forces between the chains, either by hydrogen bonding or dipole-dipole interactions. In case of polyamides (nylon), the forces are hydrogen bonding, whereas in polyesters (terylene, dacron) and polyacrylonitriles (orlon) it is dipole-dipole interactions.
11. What are the intermolecular forces in acrilan?
a) Hydrogen bonds
b) Dipole-dipole interaction between carbonyl groups
c) Dipole-dipole interaction between carbonyl and cyano groups
d) Van der Waals forces
Explanation: Acrilan is a fibre of polyacrylonitrile. It forms strong intermolecular bonds through dipole-dipole interactions between the carbonyl and cyano groups.
12. Which of the following has the weakest intermolecular forces?
Explanation: Elastomers (buna-N) have the weakest intermolecular forces whereas fibres (nylon-6,6) have very strong intermolecular forces due to hydrogen bonds and dipole-dipole forces. Thermoplastic polymers (polythene, polystyrene) have intermolecular attractions intermediate to that of elastomers and fibres.
d) thermosetting plastic
Explanation: The shown polymer is polyvinyl chloride. It is a dense linear polymer which is capable of repeatedly softening on heating and hardening on cooling.
14. ________ undergoes permanent deformation on heating.
Explanation: Bakelite is a cross-linked thermosetting polymer, which on heating undergoes extensive cross-linking and undergo permanent change. They cannot be reused.
15. Terylene is a thermoplastic polymer prepared from addition polymerisation.
Explanation: Terylene, also known as polyethylene terephthalate, is a thermoplastic polymer of the polyester family. Terylene is made from the condensation polymerisation of terephthalic acid and ethylene glycol.
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