Chapter 15: Introduction to Polymer Chemistry Mock Test
Time: 1 Hour | Maximum Marks: 25
- All questions are compulsory.
- Section A contains Q1 (Multiple Choice) and Q2 (Very Short Answer).
- Section B contains Short Answer Type I questions (2 marks each). Attempt any 4.
- Section C contains Short Answer Type II questions (3 marks each). Attempt any 2.
- Section D contains Long Answer questions (4 marks each). Attempt any 1.
SECTION A
Q1. Select and write the most appropriate answer from the given alternatives: [4 Marks]
-
Which of the following is a condensation polymer?
(A) Polythene(B) Teflon(C) Nylon-6,6(D) PVC
-
The monomer of natural rubber is:
(A) Chloroprene(B) Isoprene(C) Neoprene(D) Styrene
-
Which catalyst is used in the preparation of High-Density Polythene (HDPE)?
(A) Ziegler-Natta catalyst(B) Vanadium pentoxide(C) Nickel(D) Platinized asbestos
-
Which of the following is a biodegradable polymer?
(A) PHBV(B) Bakelite(C) Terylene(D) Polystyrene
Q2. Answer the following questions in one sentence: [3 Marks]
- Define: Elastomers.
- What is the chemical name of Teflon?
- Name the process used to improve the physical properties of natural rubber by heating it with sulfur.
SECTION B
Attempt any FOUR of the following: [8 Marks]
- Distinguish between Thermoplastic and Thermosetting polymers. (Write 2 points).
- What are copolymers? Give one example.
- Write the chemical equation for the preparation of Teflon. Mention its one use.
- Distinguish between Addition polymers and Condensation polymers. (Write 2 points).
- Write the names and structural formulas of the monomers used in the preparation of Nylon-6,6.
SECTION C
Attempt any TWO of the following: [6 Marks]
- Describe the preparation of Terylene (Dacron) with a balanced chemical equation.
- Explain the preparation of Bakelite. State its classification based on structure.
- How is Low-Density Polythene (LDPE) prepared? State any two uses of LDPE.
SECTION D
Attempt any ONE of the following: [4 Marks]
- (a) What are biodegradable polymers? Write the names of the monomers used to prepare PHBV. [3 Marks]
(b) Classify polymers on the basis of source (origin). [1 Mark] - (a) Explain the preparation of Nylon-6. Write the chemical equation. [2 Marks]
(b) Classify polymers on the basis of intermolecular forces. [2 Marks]
Solutions & Marking Scheme
SECTION A [7 Marks]
Q1. Multiple Choice Answers:
1. (C) Nylon-6,6 [1 Mark. Formed by condensation of hexamethylenediamine and adipic acid with loss of water]
2. (B) Isoprene [1 Mark. IUPAC name: 2-methyl-1,3-butadiene]
3. (A) Ziegler-Natta catalyst [1 Mark for correct option]
4. (A) PHBV [1 Mark for correct option]
Q2. Very Short Answers:
1. Elastomers:
Polymers in which the polymer chains are held together by the weakest intermolecular forces, giving them rubber-like elastic properties, are called elastomers. [1 Mark]
2. Chemical name of Teflon:
Polytetrafluoroethylene (PTFE). [1 Mark]
3. Heating rubber with sulfur:
Vulcanization. [1 Mark]
SECTION B [8 Marks]
Q3. Thermoplastic vs Thermosetting Polymers:
| Thermoplastic Polymers | Thermosetting Polymers |
|---|---|
| Soften on heating and harden on cooling reversibly. Can be reshaped and recycled. | Undergo permanent chemical change (cross-linking) on heating, becoming hard and infusible. Cannot be reshaped. |
| Structurally, they are linear or slightly branched. | Structurally, they have a heavy 3D cross-linked network. |
[1 Mark for each point of distinction. Total 2 Marks]
Q4. Copolymers:
Definition: Polymers formed by the polymerization of two or more different types of monomers are called copolymers. [1 Mark]
Example: Buna-S (formed from 1,3-butadiene and styrene), Nylon-6,6. [1 Mark]
Q5. Preparation and Use of Teflon:
Teflon is prepared by heating tetrafluoroethene gas under high pressure in the presence of a free radical initiator (like peroxides). [1/2 Mark]
$n \text{ } CF_2=CF_2 \xrightarrow{\text{Catalyst, High Pressure}} [-CF_2-CF_2-]_n$ [1 Mark]
Use: Used in making non-stick coating for cooking utensils. [1/2 Mark]
Q6. Addition vs Condensation Polymers:
| Addition Polymers | Condensation Polymers |
|---|---|
| Formed by repeated addition of unsaturated monomers without loss of by-products. | Formed by condensation of bi-functional monomers with the elimination of small molecules like $H_2O, NH_3$. |
| Molecular mass is an integral multiple of monomer mass. | Molecular mass is not an exact integral multiple due to loss of by-products. |
[1 Mark for each point of distinction. Total 2 Marks]
Q7. Monomers of Nylon-6,6:
1. Hexamethylenediamine: $H_2N-(CH_2)_6-NH_2$ [1 Mark]
2. Adipic acid (Hexanedioic acid): $HOOC-(CH_2)_4-COOH$ [1 Mark]
SECTION C [6 Marks]
Q8. Preparation of Terylene (Dacron):
Terylene is a polyester formed by the condensation polymerization of Ethylene glycol (ethane-1,2-diol) and Terephthalic acid (benzene-1,4-dicarboxylic acid) at 420-460 K in the presence of zinc acetate-antimony trioxide catalyst. Water is eliminated. [1 Mark]
$n \text{ } HO-CH_2-CH_2-OH + n \text{ } HOOC-C_6H_4-COOH \xrightarrow{420-460 \text{ K}}$
$[-O-CH_2-CH_2-O-CO-C_6H_4-CO-]_n + 2n \text{ } H_2O$
Q9. Preparation and Classification of Bakelite:
Preparation: Phenol and formaldehyde react in the presence of an acid or base catalyst to form a linear polymer called Novolac. When Novolac is further heated with hexamethylenetetramine (cross-linking agent), extensive cross-linking occurs, forming a rigid 3D solid network known as Bakelite. [2 Marks]
Classification based on structure: It is a Cross-linked (or network) polymer. [1 Mark]
Q10. LDPE Preparation and Uses:
Preparation: Low-Density Polythene is obtained by heating ethene at high temperatures (350-570 K) and very high pressures (1000-2000 atm) in the presence of traces of oxygen or peroxide as an initiator. This forms a highly branched chain polymer with low density. [1.5 Marks]
Uses: [1.5 Marks, 0.75 each]
- Used for making flexible pipes and squeeze bottles.
- Used as packaging material (plastic bags, wrapping films).
SECTION D [4 Marks]
Q11. (a) Biodegradable Polymers & PHBV [3 Marks] (b) Classification based on source [1 Mark]
(a) Biodegradable Polymers:
Polymers that can be degraded or broken down into simpler, harmless substances by the action of microorganisms (bacteria/fungi) in the environment are called biodegradable polymers. [1 Mark]
Monomers of PHBV:
- 3-Hydroxybutanoic acid [1 Mark]
- 3-Hydroxypentanoic acid [1 Mark]
(b) Classification on the basis of source:
Polymers are classified into three types: Natural polymers, Synthetic polymers, and Semi-synthetic polymers. [1 Mark]
Q12. (a) Preparation of Nylon-6 [2 Marks] (b) Classification on intermolecular forces [2 Marks]
(a) Preparation of Nylon-6:
Nylon-6 is prepared by heating $\epsilon$-caprolactam with water at a high temperature (533 K). The ring opens up to form $\epsilon$-aminocaproic acid, which undergoes self-condensation polymerization. [1 Mark]
n (Cyclic $\epsilon$-caprolactam) $\xrightarrow{H_2O, 533 \text{ K}}$ $[-NH-(CH_2)_5-CO-]_n$ (Nylon-6)
[1 Mark](b) Classification based on intermolecular forces:
Based on the magnitude of intermolecular forces, polymers are classified into four categories: [2 Marks for naming all 4]
- Elastomers (Weakest forces)
- Fibres (Strongest forces, H-bonding)
- Thermoplastic polymers (Intermediate forces)
- Thermosetting polymers (Cross-linked)
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