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Unit 2: Polymers - Practice Quiz

CHE124 — Engineering Chemistry 60 Questions
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1 A polymer is a large molecule made up of many repeating units called:

Basics of Polymer chemistry Easy
A. Catalysts
B. Isotopes
C. Monomers
D. Isomers

2 The process of joining monomers to form a polymer is called:

Basics of Polymer chemistry Easy
A. Neutralization
B. Distillation
C. Polymerization
D. Hydrolysis

3 The degree of polymerization refers to the:

Degree of polymerization Easy
A. Number of double bonds present
B. Mass of a single monomer
C. Temperature of polymerization
D. Number of monomer units in a polymer chain

4 If the molecular weight of a polymer is and the monomer (ethylene) mass is , the degree of polymerization is:

Degree of polymerization Easy
A.
B.
C.
D.

5 Based on origin, natural rubber is classified as a:

Classification of polymers Easy
A. Synthetic polymer
B. Inorganic polymer
C. Semi-synthetic polymer
D. Natural polymer

6 A polymer that softens on heating and hardens on cooling repeatedly is called a:

Classification of polymers Easy
A. Fiber
B. Thermosetting polymer
C. Thermoplastic
D. Elastomer

7 Polymers with highly ordered, closely packed chains are described as:

Molecular shape and Crystallinity Easy
A. Gaseous
B. Crystalline
C. Ionic
D. Amorphous

8 Amorphous polymers are characterized by chains that are:

Molecular shape and Crystallinity Easy
A. Randomly arranged
B. Fully crystalline
C. Perfectly ordered
D. Chemically cross-linked only

9 The glass transition temperature () is the temperature at which a polymer changes from:

Glass transition temperature (Tg) Easy
A. A hard, glassy state to a soft, rubbery state
B. A liquid to a crystal
C. A solid to a gas directly
D. An acid to a base

10 Which factor generally increases the glass transition temperature () of a polymer?

Basic factors affecting Tg (with examples, no details) Easy
A. Lower molecular weight
B. Higher chain stiffness
C. Addition of plasticizers
D. Greater chain flexibility

11 Elastomers are polymers that are known for their:

structure, synthesis and applications of elastomers and common polymers Easy
A. Brittleness and rigidity
B. High elasticity and ability to stretch
C. High crystallinity
D. Electrical insulation only

12 The monomer used to synthesize polyethylene is:

structure, synthesis and applications of elastomers and common polymers Easy
A. Ethylene
B. Vinyl chloride
C. Propylene
D. Styrene

13 PVC (polyvinyl chloride) is commonly used for making:

structure, synthesis and applications of elastomers and common polymers Easy
A. Glass windows
B. Aircraft engines
C. Pipes and electrical insulation
D. Medicines

14 Biodegradable polymers are those that can be broken down by:

biodegradable polymers: classifications, uses and methods of degradation Easy
A. Sunlight only
B. Microorganisms
C. Magnets
D. High pressure only

15 Which of the following is an example of a biodegradable polymer?

biodegradable polymers: classifications, uses and methods of degradation Easy
A. PVC
B. Polystyrene
C. Polyethylene
D. Polylactic acid (PLA)

16 Conduction in conducting polymers is mainly due to the delocalization of:

conducting polymers: p-electron delocalization, doping mechanisms, and charge carriers (solitons, polarons, bipolarons) Easy
A. Ionic bonds
B. -electrons
C. Neutrons
D. Protons

17 The electrical conductivity of a conducting polymer is increased by a process called:

conducting polymers: p-electron delocalization, doping mechanisms, and charge carriers (solitons, polarons, bipolarons) Easy
A. Distillation
B. Filtration
C. Melting
D. Doping

18 Which of the following is a common application of conducting polymers?

conductivity and transport in conducting polymers with applications in electronics, energy, and sensors Easy
A. Window glass
B. Sensors and rechargeable batteries
C. Cement
D. Cooking oil

19 The main purpose of a lubricant is to:

lubricants: lubrication and its purpose, additives for lubricants, chemical and physical properties of lubricant Easy
A. Cause corrosion
B. Increase friction between surfaces
C. Reduce friction between moving surfaces
D. Heat up the machine parts

20 Which of the following is a physical property of a lubricant?

lubricants: lubrication and its purpose, additives for lubricants, chemical and physical properties of lubricant Easy
A. Oxidation stability
B. Acidity
C. Saponification value
D. Viscosity

21 A polymer sample has a number-average molecular weight of and is made from a monomer of molecular weight . What is the degree of polymerization?

Degree of polymerization Medium
A. 2000
B. 1568000
C. 28000
D. 500

22 Why does linear high-density polyethylene (HDPE) show higher crystallinity than branched low-density polyethylene (LDPE)?

Molecular shape and Crystallinity Medium
A. Branches increase intermolecular attraction
B. Linear chains pack more closely and regularly
C. LDPE contains stronger covalent bonds
D. HDPE has a lower molecular weight

23 Below the glass transition temperature (), an amorphous polymer behaves as:

Glass transition temperature (Tg) Medium
A. A hard, brittle, glassy solid
B. A fully crystalline solid
C. A free-flowing viscous liquid
D. A soft rubbery material

24 Which change is expected to increase the of a polymer?

Basic factors affecting Tg (with examples, no details) Medium
A. Adding a plasticizer
B. Increasing chain flexibility
C. Lowering the molecular weight
D. Introducing bulky, rigid side groups

25 Vulcanization improves the properties of natural rubber mainly by:

structure, synthesis and applications of elastomers and common polymers Medium
A. Forming sulphur cross-links between chains
B. Increasing the degree of crystallinity
C. Breaking the polyisoprene chains
D. Adding oxygen to the backbone

26 Electrical conductivity in polymers like polyacetylene primarily arises from:

conducting polymers: p-electron delocalization, doping mechanisms, and charge carriers (solitons, polarons, bipolarons) Medium
A. Ionic bonding between monomers
B. Saturated -bonds throughout the chain
C. Delocalization of -electrons along the conjugated backbone
D. Movement of metal ions in the chain

27 A polaron in a conducting polymer is best described as:

conducting polymers: p-electron delocalization, doping mechanisms, and charge carriers (solitons, polarons, bipolarons) Medium
A. A pair of two positive charges
B. A free electron in a metal band
C. A radical cation coupled with a local lattice distortion
D. A neutral spinless defect

28 When two polarons of the same charge combine on a polymer chain, they form a:

conducting polymers: p-electron delocalization, doping mechanisms, and charge carriers (solitons, polarons, bipolarons) Medium
A. Soliton
B. Neutral defect
C. Bipolaron
D. Exciton

29 Polylactic acid (PLA) is classified as a biodegradable polymer mainly because it:

biodegradable polymers: classifications, uses and methods of degradation Medium
A. Contains hydrolyzable ester linkages
B. Contains only C–C single bonds
C. Has a fully aromatic backbone
D. Is cross-linked with sulphur

30 Which mechanism describes photodegradation of polymers?

biodegradable polymers: classifications, uses and methods of degradation Medium
A. Chain scission by enzymes
B. Breakdown by water absorption
C. Bond cleavage induced by UV light
D. Degradation due to applied stress

31 The main purpose of a lubricant between two moving surfaces is to:

lubricants: lubrication and its purpose Medium
A. Increase surface adhesion
B. Reduce friction and wear
C. Increase the coefficient of friction
D. Raise the operating temperature

32 Pour point depressants are added to lubricating oils to:

additives for lubricants Medium
A. Increase oil viscosity at high temperature
B. Improve the oil's flash point
C. Keep the oil fluid at low temperatures
D. Prevent oxidation of the oil

33 A high viscosity index (VI) lubricant is desirable because its viscosity:

chemical and physical properties of lubricant Medium
A. Depends only on pressure
B. Drops sharply as temperature rises
C. Increases rapidly with temperature
D. Changes little with temperature

34 Nylon-6,6 is classified as which type of polymer based on its mode of synthesis?

Classification of polymers Medium
A. Coordination polymer
B. Addition polymer
C. Free-radical polymer
D. Condensation polymer

35 In chain-growth (addition) polymerization, monomers must generally contain:

Basics of Polymer chemistry Medium
A. A metal catalyst atom
B. A reactive double bond or ring
C. Two different functional groups
D. An ester linkage

36 Compared to an amorphous polymer, a highly crystalline polymer of the same type generally shows:

Structure-property relationship Medium
A. Lower melting point
B. Reduced tensile strength
C. Greater transparency and flexibility
D. Higher density and greater rigidity

37 Which application directly uses the electrical conductivity of conducting polymers?

conductivity and transport in conducting polymers with applications in electronics, energy, and sensors Medium
A. Vulcanized tyre manufacture
B. Organic light-emitting diodes (OLEDs)
C. Food packaging films
D. Water-repellent coatings

38 Cross-linking a polymer network typically affects by:

Basic factors affecting Tg (with examples, no details) Medium
A. Eliminating it entirely
B. Lowering it due to increased free volume
C. Raising it due to restricted chain motion
D. Leaving it completely unchanged

39 An ideal elastomer must have chains that are:

structure, synthesis and applications of elastomers and common polymers Medium
A. Flexible with occasional cross-links
B. Short and completely linear
C. Rigid and highly crystalline
D. Fully cross-linked into a dense network

40 If the degree of polymerization of polystyrene (monomer mass ) is , its number-average molecular weight is approximately:

Degree of polymerization Medium
A.
B.
C.
D.

41 A sample of poly(vinyl chloride) (repeat unit mass ) has a number-average molar mass of . What is its number-average degree of polymerization?

Degree of polymerization Hard
A.
B.
C.
D.

42 Which combination of structural changes would be expected to raise the glass transition temperature () of a polymer the most?

Basic factors affecting Tg (with examples, no details) Hard
A. Adding plasticizer and increasing free volume
B. Increasing side-chain length and reducing intermolecular forces
C. Increasing chain stiffness and increasing crosslink density
D. Introducing flexible ether linkages and lowering molar mass

43 In trans-polyacetylene, a neutral soliton is best described as which of the following?

conducting polymers: p-electron delocalization, doping mechanisms, and charge carriers (solitons, polarons, bipolarons) Hard
A. A doubly charged spinless defect spanning several rings
B. A bond-alternation domain wall carrying spin but no charge
C. A pair of positive charges bound within a single benzenoid unit
D. A radical cation with both spin and charge localized on one site

44 In polymers with a non-degenerate ground state such as polypyrrole, increasing the doping level typically converts polarons into bipolarons. A bipolaron is:

conducting polymers: p-electron delocalization, doping mechanisms, and charge carriers (solitons, polarons, bipolarons) Hard
A. A singly charged species carrying spin
B. A neutral radical acting as a mobile domain wall
C. A spinless dication (or dianion) stabilized by lattice distortion
D. Two independent free electrons in the conduction band

45 Two polyethylene samples have identical molar mass. Sample X is high-density (HDPE) and Sample Y is low-density (LDPE). Which statement correctly relates their structure to density and crystallinity?

Molecular shape and Crystallinity Hard
A. X is more linear, packs more efficiently, and is more crystalline and denser than Y
B. Both have identical crystallinity because molar mass is equal
C. X is highly branched, which increases crystallinity and density
D. Y is more linear and therefore more crystalline than X

46 Isotactic polypropylene is a hard, high-melting crystalline solid, whereas atactic polypropylene is a soft, amorphous, tacky material. The primary structural reason is:

Structure-property relationship Hard
A. Regular stereochemistry in the isotactic form permits ordered chain packing into crystallites
B. The atactic form has a much higher molar mass than the isotactic form
C. The isotactic form contains extensive covalent crosslinks
D. The atactic form has stronger hydrogen bonding between chains

47 Poly(lactic acid) (PLA) and poly(glycolic acid) degrade primarily by which mechanism under physiological conditions?

biodegradable polymers: classifications, uses and methods of degradation Hard
A. Enzymatic cleavage of amide bonds only
B. Hydrolysis of ester linkages in the backbone
C. Photodegradation initiated by UV chromophores
D. Oxidative cleavage of carbon-carbon bonds

48 Charge transport in bulk conducting polymers is often limited not by intrachain motion but by:

conductivity and transport in conducting polymers with applications in electronics, energy, and sensors Hard
A. The intrinsic band gap of a perfect single chain
B. Interchain hopping and transport across disordered/amorphous regions
C. Thermal expansion of the crystalline lattice at room temperature
D. The absence of any -conjugation along the backbone

49 A lubricant with a high viscosity index (VI) is preferred because it:

lubricants: lubrication and its purpose, additives for lubricants, chemical and physical properties of lubricant Hard
A. Has very low viscosity at all temperatures
B. Becomes markedly thicker as temperature rises
C. Contains the highest possible sulfur content
D. Shows relatively small change in viscosity with temperature

50 Vulcanization of natural rubber with sulfur improves its elastic properties chiefly because sulfur:

structure, synthesis and applications of elastomers and common polymers Hard
A. Increases the degree of unsaturation in each chain
B. Fully crystallizes the amorphous rubber into a rigid solid
C. Converts the cis configuration entirely into the trans form
D. Forms crosslinks between polyisoprene chains, restoring shape after deformation

51 For a semicrystalline polymer, which statement about and is correct?

Glass transition temperature (Tg) Hard
A. Fully crystalline polymers show a sharp but no
B. and are identical for any semicrystalline polymer
C. always occurs below in semicrystalline polymers
D. is a property of the amorphous regions while is that of the crystalline regions, and

52 Bakelite (phenol-formaldehyde resin) is classified as a thermosetting polymer because:

Classification of polymers Hard
A. It forms an irreversible three-dimensional crosslinked network on curing
B. It softens repeatedly on heating and hardens on cooling
C. It consists of linear chains held only by weak van der Waals forces
D. It is a linear addition polymer with no crosslinking

53 Which of the following distinguishes a condensation (step-growth) polymerization from a chain-growth (addition) polymerization?

Basics of Polymer chemistry Hard
A. In step-growth, high molar mass polymer forms almost instantly at low conversion
B. Chain-growth requires bifunctional monomers with -COOH and -OH groups
C. Chain-growth always releases a small molecule such as water
D. In step-growth, monomers react in stages and small molecules are often eliminated; high molar mass appears only at high conversion

54 Treating polyacetylene with iodine () is an example of p-type doping. The role of iodine is to:

conducting polymers: p-electron delocalization, doping mechanisms, and charge carriers (solitons, polarons, bipolarons) Hard
A. Donate electrons to the polymer backbone, forming negative carriers
B. Form covalent C-I bonds that saturate all double bonds
C. Accept electrons from the polymer, creating positive charge carriers on the chain
D. Break the conjugation to localize electrons on individual carbons

55 In a step-growth polymerization following Carothers' equation, the number-average degree of polymerization is . To achieve , the required extent of reaction is:

Degree of polymerization Hard
A.
B.
C.
D.

56 Kevlar (poly-p-phenylene terephthalamide) has exceptional tensile strength primarily due to:

Structure-property relationship Hard
A. Random amorphous coils that dissipate stress uniformly
B. Weak dispersion forces allowing chains to slide and self-heal
C. Rigid rod-like chains aligned and held by extensive interchain hydrogen bonding
D. A highly branched network that resists any deformation

57 Under extreme pressure (EP) conditions where metal surfaces nearly touch, boundary lubrication is maintained by EP additives that:

lubricants: lubrication and its purpose, additives for lubricants, chemical and physical properties of lubricant Hard
A. Lower the pour point so oil flows at low temperature
B. Neutralize acids formed during oil oxidation
C. Increase the bulk viscosity so a thick fluid film is always present
D. React chemically with the metal surface to form a low-shear protective film

58 Which classification best fits polyhydroxyalkanoates (PHAs) such as PHB?

biodegradable polymers: classifications, uses and methods of degradation Hard
A. Naturally occurring, microbially synthesized biodegradable polyesters
B. Crosslinked thermosets requiring incineration for disposal
C. Synthetic polyamides degraded only by UV light
D. Petroleum-derived non-degradable thermoplastics

59 Adding bulky, irregular side groups along a polymer backbone generally:

Molecular shape and Crystallinity Hard
A. Decreases crystallinity by hindering regular chain packing
B. Has no effect on crystallinity, only on molar mass
C. Always converts the polymer into a perfect single crystal
D. Increases crystallinity by strengthening dipole interactions

60 PEDOT:PSS is widely used in electronics. Which pairing of material role and application is correct?

conductivity and transport in conducting polymers with applications in electronics, energy, and sensors Hard
A. Ferromagnetic core / data storage in hard drives
B. Optical fiber cladding / long-distance signal transmission
C. Transparent conductive electrode / hole-injection layer in OLEDs and flexible displays
D. High-band-gap insulator / dielectric spacer in capacitors
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