Polymers MCQ Quiz - Objective Question with Answer for Polymers - Download Free PDF

CONCEPT:

Monochlorination of Methane

• Monochlorination of methane is a free radical chain reaction that occurs in the presence of ultraviolet (UV) light or heat.
• The reaction consists of three steps: initiation, propagation, and termination.
• Initiation Step: In this step, the chlorine molecule (Cl₂) is split into two chlorine radicals (Cl•) due to the absorption of energy (UV light or heat). This step does not involve the formation of methyl radicals.
• Propagation Step: In this step, a methyl radical (CH₃•) is formed. The sequence of reactions is as follows:
  • Cl• reacts with methane (CH₄) to form a methyl radical (CH₃•) and HCl.
  • CH₃• then reacts with another Cl₂ molecule to form chloromethane (CH₃Cl) and regenerate the Cl• radical.
  This step propagates the chain reaction.
• Termination Step: In this step, two radicals combine to form a stable molecule, thereby ending the chain reaction. For example, two CH₃• radicals can combine to form ethane (C₂H₆).

EXPLANATION:

• In the given question, the formation of the methyl radical (CH₃•) occurs during the propagation step of the reaction.
• Specifically, the first propagation reaction is:

  CH₄ + Cl• → CH₃• + HCl

• This methyl radical is then used in the next propagation step to react with Cl₂, continuing the chain reaction.
• The initiation step only generates chlorine radicals, and the termination step involves the combination of radicals to form stable molecules.

Therefore, the correct answer is Option 3: Propagation step.

CONCEPT:

Ziegler-Natta Catalyst and Titanium Oxidation State

• Ziegler-Natta catalysts are widely used in the polymerization of alkenes, especially for producing polyethylene and polypropylene.
• These catalysts typically consist of a transition metal compound (e.g., titanium chloride) and an organometallic co-catalyst (e.g., alkyl aluminum compounds).
• The active site in Ziegler-Natta catalysts often involves titanium ions, which play a critical role in the polymerization process.
• The oxidation state of titanium in the catalyst can influence its ability to coordinate and insert monomers into the growing polymer chain.

EXPLANATION:

• In the case of Ziegler-Natta catalysts, titanium is generally assumed to be in the +3 oxidation state.
• This is because:
  • Titanium(III) compounds (e.g., TiCl₃) are commonly used in the preparation of these catalysts.
  • Titanium(III) has a partially filled d-orbital, which allows it to form active sites capable of coordinating alkenes and facilitating their polymerization.
• Although titanium can exist in other oxidation states (e.g., +4 in TiCl₄), the +3 oxidation state is considered the active form in Ziegler-Natta catalysis.

Therefore, the titanium ion in Ziegler-Natta catalysts is typically in the +3 oxidation state.

CONCEPT:

Co-polymer

• A co-polymer is a polymer made by the chemical bonding of two or more different types of monomers.
• These monomers are polymerized together to produce materials with combined or enhanced properties.
• Co-polymers are often designed for specific mechanical, thermal, or chemical characteristics.

EXPLANATION:

• Option 1 – PVC (Polyvinyl Chloride):
  • Formed by polymerizing only one monomer: vinyl chloride → Homopolymer 
• Option 2 – Polyethylene:
  • Made from ethylene monomers only → Homopolymer 
• Option 3 – Melamine:
  • Polymer made by polymerizing melamine and formaldehyde (a thermosetting polymer), but it is considered a condensation polymer, not specifically a co-polymer 
• Option 4 – Bakelite:
  • Formed from phenol and formaldehyde, two different monomers → Co-polymer ✅

Therefore, the correct answer is Bakelite, which is a co-polymer.

EXPLANATION:

Origin of the Word "Polymer"

• The word "polymer" is derived from the Greek language.
• It is composed of two Greek roots:
  • "Poly" meaning "many"
  • "Mer" meaning "part" or "unit"
• Therefore, "polymer" literally translates to "many parts" or "many units," which is consistent with the structure of polymers as large molecules composed of repeating subunits.
• The correct answer is "Greek" because the term "polymer" originates from the Greek words "poly" (many) and "meros" (parts).

Therefore, the word "polymer" is derived originally from the Greek language.

CONCEPT:

Polymerisation of Formaldehyde

• Formaldehyde (CH₂O) is a simple aldehyde that can undergo polymerisation under specific conditions.
• Polymerisation generally occurs at lower temperatures, as higher temperatures may favor decomposition or other reactions.
• At temperatures below 100°C, formaldehyde tends to polymerise into polyoxymethylene (a polymer chain) due to its inherent chemical reactivity.

EXPLANATION:

• Formaldehyde polymerises at temperatures below 100°C because at lower temperatures, the molecular motion is reduced, promoting interactions between molecules that lead to polymer chain formation.
• At higher temperatures, such as above 200°C or 300°C, polymerisation is less likely due to increased thermal energy, which can lead to breakdown of the polymer or other side reactions.
• Extreme temperatures, like above 500°C, would cause complete degradation of formaldehyde rather than polymerisation.
• Therefore, the correct answer is Option 1: Below 100°C, as this is the range in which formaldehyde polymerises effectively.

Therefore, formaldehyde polymerises at temperatures below 100°C.

Concept :

Thermosetting polymers: 

• A thermosetting polymer is a polymer made up of cross-linked molecules or molecules with a lot of branches.
• When heated, these soft solid or viscous polymers undergo substantial cross-linking in moulds, resulting in irreversibly hard and intractable products.

Properties of thermosetting polymers:

• One of the most important characteristics of thermoset plastics or polymers is that they harden throughout the moulding process.
• They cannot be softened once solidified.
• When polymers are moulded, they often develop a three-dimensional cross-linked structure as well as strong covalent connections.
• The covalent bonds and 3D structure enables them to retain their strength and structure even at high temperatures.
• Thermoset polymers are brittle and may char and burn if exposed to heat for an extended period of time.
• In the meanwhile, most inorganic solvents are insoluble in thermoset resins.

Examples: 

• Bakelite - 
  • A relatively poor conductor of electricity and heat.
  • It's mostly utilised to make electrical switches, as well as handles for various utensils.
• Melamine - 
  • Can withstand fire and heat.
  • It's found in cookware, clothes, and floor tiles.
• Silicones, vulcanised rubber, epoxies, polyesters, and phenolics are other examples of thermoset plastic polymers.

Explanation:

• Thermosetting polymers are those which can not be remoulded once they are formed.
• They have cross-linkages in abundance and hence get 'set' in one from when formed. 
• Examples of thermosetting polymers are bakelite, melamine, silicones, Vulcanised rubber.

Hence, as bakelite is an example of a thermosetting polymer, it is the correct answer to his question. 

1)

Explanation:- 

PAN - PAN is known as Polyacrylonitrile, Polyvinyl cyanide, Creslan 61. PAN is a copolymer made of acrylonitrile monomers. 

• Natural Rubber -  Isoprene is the monomer of natural rubber. The chemical name of isoprene is 2-methyl-1,3, butadiene

.

• Nylon-6 - Nylon-6 is made up of monomers of Caprolactam.

• PVC - The full form of PVC is Polyvinyl Chloride. It is made of the monomer units of Chloroethene or vinyl chloride.

Additional Information

•  The word ‘polymer’ is coined from two Greek words: poly means many and mer means unit or part. The process of formation of polymers from respective monomers is called polymerization. 
• The addition polymerization of acrylonitrile in presence of a peroxide catalyst leads to the formation of polyacrylonitrile.
• Polyacrylonitrile is used as a substitute for wool in making commercial fibers as orlon or Acrilan. Nylon 6 is obtained by heating caprolactam with water at a high temperature. Nylon 6 is used for the manufacture of tire cords, fabrics, and ropes. 

The correct answer is Linear polymers​.

• Linear polymers:
  • It consists of a long and straight-chain of monomers.
  • PVC is a linear polymer.
• Branched polymers: 
  • They are linear polymers containing some branches.
  • e.g Low-density Polythene.
• Network or cross-linked polymer: 
  • Polymers having cross-linked bonds with each other is called cross-linked or network polymer.
  • e.g Bakelite and melamine. 

Notes:

• PVC formation:

• Some important monomers:

The correct answer is - 2) Chloroprene

Concept

Polymer - The term polymer in Greek means 'many parts. 

• A polymer is a large molecule or a macromolecule which is basically a combination of many subunits.
• These subunits which form a polymer are known as monomers.
• Polymers may be naturally found in plants and animals (natural polymers) or they are man-made(synthetic polymers).
• Different polymers have unique physical and chemical properties.

​Synthetic rubbers- These are artificial elastomers.

• They are the polymers that are synthesized from petroleum byproducts.

Explanation:

Neoprene - It is also called polychloroprene or chloroprene rubber.

• It is the synthetic rubber produced by the polymerization of chloroprene.
• It's valued for its high tensile strength, oil and flame resistance, and resistance to degradation by oxygen and ozone.

Concept:

Polymer 

• Compounds consist of long-chain molecules, in which each molecule is made up of 100-10000 repeating units connected together. 
• Its molar mass ranges from 10⁴ - 10⁶ g/ g-mole
• Polymers may be naturally occurring or man-made. 

Orlon

• Orlon is an acrylic fibre, which is resistant to sunlight and atmospheric gases. 
• It has good thermal stability. 
• The fibre has good elasticity and low moisture absorption.

Teflon

• Teflon is a synthetic fluoropolymer made up of tetrafluoroethylene monomer.
• It is a thermoplastic polymer.
• Good chemical resistance and good resistance to light, UV and weathering. 
• Low water absorption. 

Decron

• Dacron is a condensation polymer made by the condensation of ethylene glycol and terephthalic acid. 
• It has high tensile strength and high resistance to stretching. 

Melamine

• Melamine resin or melamine formaldehyde is a hard, highly durable and versatile thermosetting aminoplast known best for its resistance to heat and fire. 
• The fibre is chemically inert, non-flammable, non-toxic and has no degradation up to 200⁰ C. 

Explanation:

So, the correct order is option 1 ) a - 1, b - 3, c - 4, d - 2

Concept:

• The plastic which gets deformed easily on heating and can be bent easily are known as Thermoplastics. Polythene and PVC are some of the examples of Thermoplastics.
• Thermoplastics are used for manufacturing toys, combs and various types of containers.
• The plastics which keeps its shape and does not soften i.e the plastics which when moulded once, can not be softened by heating are called Thermosetting plastics.
• Thermosetting plastics are synthesized by condensation polymerization and have primary bonds between molecular chains and held together by strong cross links.
• Thermosetting plastics have a high melting point and tensile strength as compared to thermoplastics.

The correct answer is - 4) C6H5OH and HCHO

Concept:

Polymer - The term polymer in Greek means 'many parts'. 

• A polymer is a large molecule or a macromolecule which is basically a combination of many subunits.
• These subunits which form a polymer are known as monomers.
• Polymers may be naturally found in plants and animals (natural polymers) or they are man-made(synthetic polymers).
• Different polymers have unique physical and chemical properties.
• There are mainly two methods of polymerization which are-

1. Addition polymerization
2. Condensation polymerization

Explanation:

Condensation polymerization- It is a form of step-growth polymerization in which monomers or oligomers react with each other to form large structural units(usually polymers) while releasing smaller molecules as a byproduct(such as water or methanol).

• Examples- Nylon-6,6, bakelite, etc.
• The monomers should have one or two functional groups.
• Condensation polymers form more slowly than addition polymers.
• They are generally lower in molecular weight.

Bakelite is a condensation polymer of formaldehyde (HCHO) and phenol(C₆H₅OH).

Additional Information Addition Polymerization - In this, the monomer molecules are bonded together without the loss of any byproducts.

• It is sometimes known as chain-growth polymerization.
• Examples- Polyethylene, Polyvinyl chloride(PVC), etc.

The correct answer is Bakelite.

Key Points

• Bakelite:
  • Pressure cooker handles are made up of Bakelite; a thermosetting plastic. Hence, Option 4 is correct.
  • Bakelite is used because it has heat-resistant properties and is an electrical insulator.
  • Bakelite is a polymer made up of the monomers phenol and formaldehyde.
  • This phenol-formaldehyde resin is a thermosetting polymer.
  • We cannot deny the presence of polymers in our lives.
  • We are surrounded by objects, most of which, some way or the other have a polymer associated with them.
  • The ease of molding polymers into different shapes and their relatively low cost of production has been the main reason for their universal usage.
  • As such, Bakelite is one of the commercially manufactured polymers that we witness in our daily lives.
  • Bakelite is the commercial name for the polymer obtained by the polymerization of phenol and formaldehyde.
  • These are one of the oldest polymers that were synthesized by man.
  • Phenol is made to react with formaldehyde.
  • The condensation reaction of the two reactants in a controlled acidic or basic medium results in the formation of ortho and para hydroxymethyl phenols and their derivatives.

Additional Information

• Polyethylene or polythene:
  • It is the most common plastic in use today.
  • It is a polymer, primarily used for packaging.
  • As of 2017, over 100 million tonnes of polyethylene resins are being produced annually, accounting for 34% of the total plastics market. 
  • Formula: (C₂H₄)ₙ
  • Melting point: 115 - 135 °C (239 - 275 °F; 388 - 408 K)
  • Density: 0.88 - 0.96 g/cm³
  • Magnetic susceptibility (χ): -9.67×10⁻⁶ (HDPE, SI, 22 °C)
  • Abbreviations: PE
• Polyethylene terephthalate
  • It is commonly abbreviated PET, PETE, or the obsolete PETP or PET-P is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing.
  • Density: 1.38 g/cm³
  • Formula: (C₁₀H₈O₄)_n
  • Melting point: 260 °C
• Nylon
  • It is a generic designation for a family of synthetic polymers composed of polyamides.
  • Nylon is a silk-like thermoplastic, generally made from petroleum, that can be melt-processed into fibers, films, or shapes.
  • Compared to other general-purpose thermoplastic resins, nylon has a very high melting point.
  • The melting point of nylon 66 is 255°C, nylon 6 is 225°C and nylon 610 is 220°C.

The correct answer is Rayon.

Key Points

• A Synthetic Fibre called Rayon is created by chemically treating Cellulose, a Natural Raw Material.
  • Wood Pulp is where the cellulose needed to make rayon is found.
  • Wood Pulp is dissolved in an Alkaline Solution to form sticky liquid called Viscose.
  • Viscose is forced to pass through the tiny holes of metal cylinder into a solution of Sulphuric Acid when a silk like thread of rayon is formed.
  • ​Rayon is made from naturally occurring polymer present in wood pulp, therefore rayon is neither a fully synthetic nor a fully natural fibre. It is a semi-synthetic fibre.

Additional Information

• Nylon
  • A condensation reaction between an acid monomer and an amine monomer produces the polymer nylon.
  • This Synthetic Fibre is both durable and light.
  • This sort of fibre is made without the use of any raw plant or animal components.​ 
• Polymer
  • It is a by product of the condensation of an alcohol monomer and an acid.
• Multiple polyester bonds are produced by the acid and alcohol's repeating unit.
  • Terephthalic acid and ethylene glycol are employed as the building blocks.

Condensation Polymers: The condensation polymers are formed by repeated condensation reaction between two different bi-functional or tri-functional monomeric units. In these polymerisation reactions, the elimination of small molecules such as water, alcohol, hydrogen chloride, etc. take place. The formation of terylene or dacron by the interaction of ethylene glycol and terephthalic acid is an example of this type of polymerisation as shown in the diagram:

Note that: Polyethylene terephthalate (sometimes written poly(ethylene terephthalate)), commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, thermoforming for manufacturing, and in combination with glass fibre for engineering resins.

Hence, we conclude that the formation of terylene or dacron takes place by the interaction of ethylene glycol and terephthalic acid.