CBSE Class 12 Chemistry Polymers Assignment

COAL, PETROLEUM AND POLYMERS

Question. When formaldehyde is heated with phenol in the presence of an alkali, the product formed is -
(A) rubber
(B) bakelite
(C) chloroprene
(D) neoprene
Answer. B

Question. Synthetic fibres are obtained from -
(A) plants
(B) animals
(C) petroleum
(D) minerals
Answer. C

Question. The monomer of Buna-S are -
(A) styrene and butadiene
(B) isoprene and butadiene
(C) vinyl chloride and sulphur
(D) butadiene.
Answer. A

Question. Which of the following substances is used in refining of petroleum ?
(A) NaCl
(B) NaOH
(C) Na₂CO₃
(D) NaHCO₃
Answer. B

Question. Which of the following is used as an anti - knocking compound ?
(A) TEL
(B) C₂H₅OH
(C) Glyoxal
(D) Freon
Answer. A

Question. Separation of fractions of petroleum is done by-
(A) simple distillation
(B) destructive distillation
(C) fractional distillation
(D) sedimentation
Answer. C

Question. Out of the different types of fuels the one which is excellent is :
(A) the solid fuel
(B) the liquid fuel
(C) the gaseous fuel
(D) none of these
Answer. C

Question. When a well is drilled through the rock, ________ comes out first.
(A) petroleum
(B) natural gas
(C) crude oil
(D) residual oil
Answer. B

Question. Which of the following is correct ?
(A) LPG is liquefied isobutane
(B) LPG is liquefied methane
(C) LPG is liquefied methane and propane
(D) LPG is mixture of methane and ethane
Answer. A

Question. While leakage in L.P.G. gas cylinders which gas gives fowl smell -
(A) butane
(B) propane
(C) methane
(D) ethyl mercaptan
Answer. D

Question. Which of the following names represents the foul smelling, black, thick, viscous liquid obtained from destructive distillation of coal ?
(A) Coke
(B) Coal tar
(C) Coal gas
(D) None of these
Answer. B

Question. Kerosene is a mixture of -
(A) alkanes
(B) aromatic compounds
(C) alcohols
(D) aliphatic acid
Answer. A

Question. The petroleum product that has replaced coal-tar for metalling the road is :
(A) peat
(B) bitumen
(C) lignite
(D) anthracite
Answer. B

Question. Coal is a fossil fuel and it cannot be prepared in a laboratory or industry because the formation of coal.
a. is very slow process.
b. needs very low pressure and low temperature.
c. needs very high pressure and high temperature.
d. causes air pollution.
Select the correct alternative.
(A) a and b
(B) b and d
(C) c and a
(D) d and c
Answer. C

Question. Which of the following products obtained by destructive distillation of coal is not properly matched ?
(A) Coal tar - Dyes, explosives, paints.
(B) Coal gas - Fuel.
(C) Coke - Drinking purposes.
(D) Ammoniacal liquor - Fertilizers.
Answer. C

Question. Natural rubber is heated with an element X to make it hard , strong and more elastic . X is :
(A) zinc
(B) sulphur
(C) lead
(D) H₂
Answer. B

Question. Which of the following are linear polymers ?
(A) Cellulose
(B) Natural Rubber
(C) Both (A) & (B)
(D) None of these
Answer. C

19. The structure of isoprene is :-
(A) CH₂= C (C₂H₅) – CH = CH₂
(B) CH₂= C (OCOCH₃) – CH = CH₂
(C) CH₂= C (CH₃) – CH = CH₂
(D) CH₂ = CH – C Ξ CH
Answer. C

Question. Correct order of products in which they are extracted from crude oil in fractional distillation column from top to bottom is -
(A) Natural gas , Petrol , Diesel , Paraffin
(B) Natural gas , Diesel , Petrol , Paraffin
(C) Natural gas , Parafin , Diesel , Petrol
(D) Parafin , Natural gas , Petrol , Diesel
Answer. A

Question. Main constituents of coal gas are -
(A) H₂O, C₂H₆, O₂
(B) CH₄, CO₂, O₂
(C) CH₄, H₂, CO
(D) C₂H₆, N₂, O₂
Answer. C

Question. Producer gas is a mixture of :
(A) CO and H₂
(B) CO and N₂
(C) Co and H₂
(D) none of these
Answer. B

Question. The head of a safety match contains
(A) antimony trisulphide and potassium chlorate.
(B) antimony chloride and potassium sulphide.
(C) antimony carbonate.
(D) potassium sulphide.
Answer. A

Question. Pick out the incorrect statement amongst the following
(A) Nylon clothing can stand high temperature and are therefore good to wear in summers.
(B) Thermosetting plastics do not become soft on heating.
(C) Addition polymers are formed without the elimination of by- product molecules.
(D) Natural rubber is obtained as latex from rubber trees.
Answer. A

Question. Rubber is heated with sulphur and the process is known as -
(A) galvanization
(B) vulcanization
(C) bessemerization
(D) sulphonation
Answer. B

Question. Thermoplastics are -
(A) linear polymers.
(B) soften or melt on heating.
(C) molten polymer can be moulded in desired shape.
(D) All of these
Answer. D

Question. Which of the following acids is used in preparation of Nylon -66 ?
(A) Acetic acid
(B) Ascorbic acid
(C) Adipic acid
(D) Amino acid
Answer. C

Question. Natural rubber is a polymer of -
(A) butadiene
(B) ethene
(C) styrene
(D) isoprene
Answer. D

Question. Match the terms of column A correctly with the phrases given in column B.
Column-A               Column-B
(i) Polyester         (a) Prepared by using wood pulp
(ii) Teflon             (b) Used for making parachutes and stockings
(iii) Rayon            (c) Electrical switches
(iv) Nylon            (d) Fabrics do not wrinkle easily
(v) Bakelite          (e) Fire - resistant clothes
(vi) Melamine       (f) Used to make non-stick cookwares
(A) (i) (d), (ii) (f), (iii) (a), (iv) (b), (v) (c), (vi) (e).
(B) (i) (f), (ii) (d), (iii) (a), (iv) (b), (v) (c), (vi) (e).
(C) (i) (d), (ii) (f), (iii) (b), (iv) (a), (v) (c), (vi) (e).
(D) (i) (a), (ii) (f), (iii) (d), (iv) (b), (v) (c), (vi) (e).
Answer. A

Question. Match the column A and B
Column A                                 Column B
i. Thermoplastics                    a. Handles of  utensils, floor tiles
ii. Thermosetting plastics         b. Melamine
iii. Biodegradable                    c. Teflon
iv. Fire proof plastic                d. Wood
v. Oil and water do not stick.   e.Combs,containers
(A) i-d, ii-e, iii-a, iv-b, v-c
(B) i-e, ii-a, iii-d, iv-b, v-c
(C) i-a, ii-d, iii-b, iv-c, v-e
(D i-c, ii-b, iii-a, iv-e, v-d
Answer. B

Question. Condensation polymer among the following is -
(A) teflon
(B) polystyrene
(C) PVC
(D) dacron
Answer. D

Question. Which of the following is not an example of synthetic fibre ?
(A) Rayon
(B) Nylon
(C) Polyacrylonitrile
(D) Fullerene
Answer. D

Question. Buna–S is -
(A) artificial fibre
(B) plastic
(C) synthetic rubber
(D) synthetic detergent
Answer. C

Question. Fuel which contains 90 % methane is -
(A) oil gas
(B) Biogas
(C) liquefied petroleum gas
(D) natural gas
Answer. D

Question. Formula of Freon-11 is - 
(A) CCl₃ F
(B) CCl₂ F₂
(C) Cl₃C–CCl₂ F
(D) CCl₂F CCl₂F
Answer. A

Question. The Freon containing two carbon atoms, two fluorine atoms and four chlorine atoms is -
(A) Freon- 112
(B) Freon- 114
(C) Freon- 113
(D) Freon- 111
Answer. A

Question. Method used for purifying petroleum is -
(A) simple distillation
(B) steam distillation
(C) vacuum distillation
(D) fractional distillation
Answer. D

Question. Among the following compounds which one is used for cooling refrigerator ?
(A) NH₄ Cl
(B) CO
(C) NH₄OH
(D) Liquid NH₃
Answer. D

Question. In the process of vulcanization -
(A) natural rubber is heated with sulphur
(B) natural rubber is heated with carbon
(C) natural rubber is heated with phosphorus
(D) natural rubber is heated with sodium
Answer. A

Question. Which gas will probably be important energy source for future ? 
(A) Methane
(B) Natural Gas
(C) Dihydrogen
(D) Nitrogen
Answer. B

Question. Which is the important constituent (95%) of natural gas ? 
(A) Methane
(B) Propane
(C) Ethane
(D) Chlorine
Answer. A

Question. Which of the following is thermoresistant polymer ? 
(A) Orlon
(B) Polythene
(C) Teflon
(D) Bakelite
Answer. D

Question. Which of the following is known as Freon ?
(A) CCl₂F₂
(B) CHCl₃
(C) CH₂F₂
(D) CF₄
Answer. A

Level-1: Questions

1) What are polymers?
Answer: These are referred to as Macromolecules which are formed by joining of repeating structural units on a large scale.
In simple words: Polymers are large molecules made up of many smaller repeating units joined together.

Exam Tip: Remember the term macromolecule and repeating structural units (monomers) for scoring keywords.

2) Give two examples each of natural and of synthetic polymers.
Answer:
Natural polymers e.g.: Proteins, starch
Synthetic polymers e.g.: Polythene, Nylon-6,6
In simple words: Natural polymers come from nature (like plants and animals), while synthetic polymers are man-made in laboratories.

Exam Tip: Always provide clear examples with correct spellings like Nylon-6,6.

3) What are biodegradable polymers? Give one example.
Answer: Polymers which are degraded easily by environmental processes.
e.g.: PHBV
In simple words: Biodegradable polymers can be broken down by microorganisms in the environment.

Exam Tip: PHBV is a very common example of a biodegradable polyester used in packaging and medicine.

4) How are the polymer classified on the basis of structure?
Answer: They are of three types based on the structure of polymers:
a) Linear polymers
b) Branched polymers
c) Cross-linked polymers
In simple words: Based on how the monomer chains are arranged, polymers are classified into straight lines, branches, or cross-linked networks.

Exam Tip: List all three structural categories clearly for full marks.

5) Define the term 'polymerisation'.
Answer: The process of making polymer from monomers.
In simple words: Polymerisation is the chemical reaction where small molecules (monomers) join together to form a giant molecule (polymer).

6) What are the monomers for the following polymers: i) Polythene ii) PVC iii) Teflon iv) Polystyrene
Answer:
i) Polythene - Ethene
ii) PVC - Vinyl chloride
iii) Teflon - Tetrafluoroethene
iv) Polystyrene - Styrene
In simple words: Each polymer gets its name from its starting monomer unit by adding 'poly' in front.

Exam Tip: Learn both common and IUPAC names of monomers.

7) In which classes, the polymers are classified on the basis of molecular forces?
Answer: Elastomers, Fibres, Thermoplastic and Thermosetting polymers.
In simple words: Polymers are grouped based on how strongly the individual polymer chains stick together.

Exam Tip: This classification depends on intermolecular forces like hydrogen bonding or dipole-dipole interactions.

8) Give an example of elastomer.
Answer: Neoprene
In simple words: Elastomers are rubber-like solids that can stretch and return to their original shape.

Exam Tip: Buna-S, Buna-N, and Neoprene are standard examples.

9) Identify the polymer. -A-A-A-A-A-
Answer: Homopolymer
In simple words: A polymer made from only one type of repeating monomer unit is a homopolymer.

10) Define the term "homopolymerisation".
Answer: The process of making polymer by adding one kind of monomers.
In simple words: Homopolymerisation involves the polymerization of only a single species of monomer.

Exam Tip: Emphasize "one kind of monomer".

11) Identify the polymer. -A-B-A-B-A-B-A-B-
Answer: Copolymer
In simple words: A polymer made from two different types of alternating monomer units is a copolymer.

Exam Tip: Alternating or mixed units indicate copolymerisation.

12) Why rubbers are called "Elastomers"?
Answer: They can be stretched and retract to its original position after the release of force.
In simple words: They act like elastic springs because of weak intermolecular forces allowing flexible coiling.

Exam Tip: Mention elasticity and recovery upon force removal.

13) Differentiate between Thermoplastic and Thermosetting polymers.
Answer:
Thermoplastic polymers: They can be reshaped again and again.
Thermosetting polymers: Once it is moulded and it cannot be remelted and reused.
In simple words: Thermoplastics soften on heating and harden on cooling repeatedly, while thermosetting plastics undergo permanent chemical changes on heating and cannot be reused.

Exam Tip: Mention reusability and cross-linking differences.

14) Is \(-NH-CHR-CO-\)_n a homopolymer or copolymer?
Answer: It is a homopolymer.
In simple words: Although it contains multiple atoms, the repeating unit is derived from a single amino acid monomer.

15) What is vulcanized rubber?
Answer: Adding sulphur to rubber to make it hard called 'Vulcanised rubber'.
In simple words: Vulcanization cross-links natural rubber with sulfur to improve its strength and elasticity.

Exam Tip: Mention sulfur cross-linking.

16) How can natural rubber be made more tough?
Answer: By adding Sulphur.
In simple words: Heating natural rubber with sulfur introduces cross-links that make it tougher and less sticky.

Exam Tip: State the process of vulcanization using sulfur.

17) What are natural polymers?
Answer: Polymers mostly found in plants and animals.
In simple words: Polymers that occur naturally in living organisms are called natural polymers.

Exam Tip: Give examples like cellulose, starch, and proteins.

18) What are synthetic polymers?
Answer: Man-made polymers.
In simple words: Synthetic polymers are artificially prepared in industries or laboratories from petrochemicals.

Exam Tip: Mention human-made origin.

19) What are polyamides and polyesters? Give one example of each.
Answer: Polyamides are polymers made with amide linkages and polyesters are polymers made with ester linkages.
Examples: Polyamide - Nylon-6,6; Polyester - Dacron (Terylene).
In simple words: Polyamides contain repeating amide groups (\(-CONH-\)), while polyesters contain repeating ester groups (\(-COO-\)).

Exam Tip: Linkage type is the key differentiator here.

20) Classify the following as homopolymers and copolymers: Polythene, PVC, PTFE, Buna-S, polystyrene, Buna-N
Answer:
Homopolymers: Polythene, PVC, PTFE, Polystyrene
Copolymers: Buna-S and Buna-N
In simple words: Homopolymers are made from one monomer type, whereas Buna-S and Buna-N are made from two different monomers.

Exam Tip: Buna rubbers always contain 1,3-butadiene plus a second monomer (styrene or acrylonitrile), making them copolymers.

Level-2: Questions

1) Explain the term 'Copolymerisation' and give two examples.
Answer: The polymerization in which Polymer is made up of two different monomer units are called copolymers. Examples: Buna-N, Buna-S.
In simple words: Copolymerisation involves reacting two different monomers together to form a single polymer chain.

Exam Tip: Clearly state that two different monomers are involved.

2) Give the monomers for the following polymers: Buna-N, Buna-S, natural rubber, Neoprene
Answer:

Exam Tip: Memorize these four standard rubber monomers as they frequently appear in board exams.

3) Discuss the main purpose of vulcanization of rubber.
Answer: Natural rubber becomes soft at high temperature, brittle at low temperature and show higher water absorption capacity. It is nonresistant to attack by oxidizing agent. In order to improve these properties a process of vulcanization is carried out.
In simple words: Vulcanization improves strength, elasticity, and resistance to heat and chemicals.

Exam Tip: List improved tensile strength, temperature range, and chemical resistance.

4) Classify the following as addition and condensation polymer: PHBV, Dacron, Teflon, neoprene, PVC, Bakelite.
Answer:
Addition polymers: Teflon, Neoprene, PVC
Condensation polymers: PHBV, Dacron, Bakelite
In simple words: Addition polymers add monomers without losing small molecules, whereas condensation polymers eliminate small molecules like water or alcohol during formation.

Exam Tip: Check whether small molecules are eliminated during polymerization.

5) Arrange the following polymers in increasing order of their inter molecular forces:
a) PVC, Natural rubber, Terylene
b) Nylon-6,6, Neoprene, PVC
c) Nylon-6, Buna-N, Teflon
Answer:
a) Natural rubber < PVC < Terylene
b) Neoprene < PVC < Nylon-6,6
c) Buna-N < Teflon < Nylon-6
In simple words: Elastomers have the weakest forces, plastics/PVC have intermediate forces, and fibers like Nylon and Terylene (with strong hydrogen bonding) have the strongest intermolecular forces.

Exam Tip: Recall the order: Elastomers < Plastics < Fibres.

6) (a) Write the structures of the monomers of Dacron. (b) Give one example of a synthetic rubber. (c) Arrange the following polymers in the increasing order of tensile strength Nylon-6, Buna-S, Polythene.
Answer:
(a) Monomers of Dacron are Ethylene glycol (\(HO-CH_2-CH_2-OH\)) and Terephthalic acid (\(HOOC-C_6H_4-COOH\)).
(b) Buna-N (or Neoprene, Buna-S)
(c) Buna-S < Polythene < Nylon-6
In simple words: (a) Dacron is made from ethylene glycol and terephthalic acid. (b) Buna-S is synthetic rubber. (c) Fibres have higher tensile strength than plastics, which have higher strength than elastomers.

Exam Tip: Tensile strength follows the order: Elastomers < Thermoplastics < Fibres.

7) Give the name and structure of reagent used for initiating a free radical chain reaction.
Answer: Benzoyl peroxide, structure: \(C_6H_5CO-O-O-COC_6H_5\).
In simple words: Benzoyl peroxide readily splits into free radicals to start addition polymerization.

8) Arrange the following polymers in increasing order of their intermolecular forces: Nylon-6, Neoprene, polyvinyl chloride.
Answer: Neoprene < Polyvinyl chloride < Nylon-6
In simple words: Elastomer (Neoprene) has the weakest forces, thermoplastic (PVC) is intermediate, and polyamide (Nylon-6) has strong hydrogen bonding.

Exam Tip: Hydrogen bonding in polyamides provides the highest intermolecular force among these three.

9) How is dacron obtained from ethylene glycol and terephthalic acid?
Answer: It is the condensation product of ethylene glycol and terephthalic acid carried out at 420 to 460K in the presence of catalyst mixture of zinc acetate and antimony trioxide.
In simple words: Heating ethylene glycol and terephthalic acid together with a catalyst forms the polyester Dacron with elimination of water.

Exam Tip: Mention temperature (420-460K) and catalyst (zinc acetate - antimony trioxide).

10) Write names of monomers of the following polymers: a) \((-CF_2-CF_2-)_n\) b) \((CH_2-CH(Cl)-)_n\).
Answer:
a) Tetrafluoroethene
b) Vinyl chloride
In simple words: (a) Teflon comes from tetrafluoroethene. (b) PVC comes from vinyl chloride.

Exam Tip: Remove the brackets and subscript \(n\) to easily find the monomer formula.

Level-3 Questions

1. What is the main constituent of bubble gum?
Answer: Styrene-butadiene copolymer (SBR).
In simple words: Bubble gum uses synthetic rubber elastomers like SBR to give it chewy properties.

Exam Tip: SBR stands for Styrene Butadiene Rubber.

2. What is a plasticizer?
Answer: The substances which are added to increase the softness of hard polymers.
In simple words: Plasticizers are additives mixed into rigid plastics to make them flexible.

Exam Tip: Phthalates are common examples of plasticizers.

3. Draw the structures of the monomer of PAN.
Answer: Monomer of PAN (Polyacrylonitrile) is Acrylonitrile, structure: \(CH_2=CH-CN\).
In simple words: Polyacrylonitrile is formed by the addition polymerization of vinyl cyanide (acrylonitrile).

4. Give the name of polymer which is used for making non-stick utensils.
Answer: Teflon (\((CF_2=CF_2)_n\)).
In simple words: Polytetrafluoroethylene (Teflon) has a slippery, heat-resistant surface ideal for non-stick pans.

Exam Tip: Remember Teflon's chemical name: Polytetrafluoroethene.

5. What is the % of sulphur using during in vulcanization of rubber?
Answer: 3% to 5%
In simple words: About 3% to 5% sulfur is added to create cross-links during rubber vulcanization.

6. Give the common and the IUPAC name of the monomer of natural rubber.
Answer: Common name: cis-Isoprene; IUPAC name: 2-methyl-1,3-butadiene.
In simple words: Natural rubber is a polymer made from isoprene units arranged in a cis configuration.

Exam Tip: Always specify 'cis' for natural rubber isomerism.

7. Discuss the two main purpose of vulcanization of rubber.
Answer:
(i) It makes the rubber hard and durable.
(ii) It increases elasticity over a wider temperature range.
(iii) It provides more wear and tear resistance.
In simple words: Vulcanization improves mechanical strength and prevents rubber from becoming too sticky when hot or brittle when cold.

8. Explain the term Thermosetting polymers and give one example.
Answer: Thermo setting polymers: These polymers are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and again become infusible. These cannot be reused. Example: Bakelite.
In simple words: Thermosetting plastics set permanently into shape when heated and cannot be melted down again.

Exam Tip: Emphasize that they cannot be remelted or reshaped.

9. Why should one always use purest monomer in free radical polymerisation?
Answer: Impurities of other substances if present, may inhibit or hinder the chain propagation.
In simple words: Impurities react with free radicals and stop the polymer chain from growing properly.

Exam Tip: Mention chain termination or inhibition by impurities.

10. How is dacron obtained from ethylene glycol and terephthalic acid?
Answer: It is the condensation product of ethylene glycol and terephthalic acid carried out at 420 to 460K in the presence of catalyst mixture of zinc acetate and antimony trioxide.
In simple words: Heating the two monomers together under specific temperature and catalytic conditions yields Dacron.

Exam Tip: Reiterate reaction conditions (420-460K, zinc acetate/antimony trioxide) for complete accuracy.