Chemistry NCERT Exemplar Solutions Class 12th Chapter Fifteen: Overview, Questions, Preparation

This is a Long Answer Type Questions as classified in NCERT Exemplar

1.Poly-hydroxybutyrate-co-β-hydroxyvalerate (PHBV)

It's made by copolymerization 3-hydroxybutanoic acid and 3-hydroxypentanoic acid. PHBV is used in specialty packaging, orthopaedic devices, and controlled drug release. In the environment, PHBV is degraded by bacteria.

Nylon 2-Nylon 6: It is a biodegradable alternating polyamide copolymer of glycine and amino caproic acid.

Biopolymers are natural polymers found in plants and animals such as protein, fat, cellulose, and so on.

Biodegradable polymers are polymers that contain functional groups that are similar to those found in biopolymers. They are not resistant to the processes of environmental degradation.

This is a Long Answer Type Questions as classified in NCERT Exemplar

In rubber, the polymer chain are held together by the weakest force of attraction. While, in plastic, the strong intermolecular force of attraction is present between elastomers and fibres.

In rubber, a few crosslinks are introduced between the chain, while plastics are linear or slightly branched molecules which gets soft on heating and hard on cooling.

This is a Long Answer Type Questions as classified in NCERT Exemplar

The oldest synthetic polymers are phenol-formaldehyde polymers. These are made by combining phenol and formaldehyde in the presence of either an acid or a base catalyst. The reaction begins with the formation of o-and/or p hydroxymethyl phenol derivatives, which then react with phenol to form compounds with shaving rings connected by –CH₂ groups. The first product could be a linear product, such as Novolac.

When heated with formaldehyde, Novolac crosslinks to form Bakelite, an infusible solid mass.

It is used to make combs, phonograph records, electrical switches, and utensil handles.

The polymer A is Novolac and polymer B is Bakelite. 

This is a Long Answer Type Questions as classified in NCERT Exemplar

Ans:

This is a Long Answer Type Questions as classified in NCERT Exemplar

Thermoplastic polymer

Thermoplastic polymers are linear or slight branched-chain polymers. In this type of polymer, the strong intermolecular force of attraction is present between elastomers and fibers. This type of polymer softens on heating and hardens on cooling. For example, polythene, polystyrene and polyvinyl.

Thermosetting polymer

Thermosetting polymers are cross-linked polymers. These polymers on heating undergo cross-linking in molds. They become infusible on heating so, cannot be reused again. For example, Bakelite and urea-formaldehyde resins.

$C{H}_4+2O_2\to C{O}_2+2H_{2}O$

Mole $\frac{100}{16}\frac{208}{32}$

$\begin{array}{l}\downarrow \downarrow \\ 6.256.5(Here{O}_{2}isthelimitingreagent)\end{array}$  

Hence mole of CO₂ formed = $\frac{6.5}{2}$  

And wt of CO₂ in gm = $\frac{6.5}{2}\times 44=143g$  

After removal A = 4 - $\left(\frac{1}{2}*2\right)=3$  

              After removal B = 4 – 1 = 4 (only two atoms are removed)

              Final formula of the compound = A₃B₄

Water has only two lone pair and XeF₄ has two lone pair electron in opposite plane of the central atom.

Vapourisation of $H_{2}O,H_2{O}_{\left(\mathcal{l}\right)}\to H_2{O}_{\left(g\right)}$  

Mole of H₂O = $\frac{36}{18}=2mol$  

$\Delta E=\Delta H-\Delta nRT$  

$=41.1-\frac{1\times 8.31\times 373}{1000}=38kJ/mole$  

$\pi =i\times c\times R\times T=\frac{2\times 0.83\times 300}{60\times 10^3}=0.00415bar$

= 415 Pa

$Hl?\frac{1}{2}{H}_2+\frac{1}{2}{l}_2$

t = eq    1 - a       $\frac{\alpha }{2}$         $\frac{\alpha }{2}\left[\alpha =0.4\right]$  

              $Kp=\frac{{\left(P_{H_2}\right)}^{\frac{1}{2}}\times {\left(P_{l_2}\right)}^{\frac{1}{2}}}{P_{Hl}}=\frac{{\left(0.2\right)}^{\frac{1}{2}}\times {\left(0.2\right)}^{\frac{1}{2}}}{0.6}$  

              = $-8.31\times 300\times 2.3\times log\left(\frac{1}{3}\right)=2735J/mol$  

cell reaction is ;

              $Cu\left(s\right)+S{n}_{\left(aq\right)}^{2+}\to C{u}_{\left(aq\right)}^{++}+S{n}_{\left(s\right)}$  

              $Q=\frac{\left[C{u}^{++}\right]}{\left[S{n}^{++}\right]}=\frac{0.01}{0.001}andn=2$  

              $E_{cell}=E_{cell}^o-\frac{0.059}{2}log\frac{0.01}{0.001}$  

              $=-0.48-\frac{0.059}{2}log10=-0.509$  

              $=983.33\times 10^{-1}KJ/mole$  

              Nearest integer = 983

$K_{cat}=A{e}^{-}\frac{{\left(Ea\right)}_{cat}}{RT}and{K}_{uncat}=A{e}^{-}\frac{{\left(Ea\right)}_{uncat}}{RT}$

 $\frac{K_{cat}}{K_{uncat}}=e^{\frac{{\left(Ea\right)}_{uncat}-{\left(Ea\right)}_{cat}}{RT}}=e^{\frac{10\times 1000}{8.314\times 300}}=e^{4.009}=e^x$

$\therefore x=4$

${\left[Co{\left(H_{2}O\right)}_6\right]}^{2+}+N{H}_{3\left(excess\right)}\to \underset{Diamagneticnature}{{\left[Co{\left(N{H}_3\right)}_6\right]}^{3+}+6H_{2}O}$

$C{o}^{3+}\to 3d^{6}4s^0$

$\Rightarrow {t_{2g}}^{6}e{g}^0$

$\Rightarrow {t_{2g}}^{6}e{g}^0$ (form of paired electron)

              No. of electron in t_2g = 6

$C{H}_4+2O_2\to C{O}_2+2H_{2}O$

2 moles of water produced by 1 mole of methane

Or 36 gm of water produced by 1 mole of CH₄

$\therefore$  81 gm of water produced = $\frac{1\times 81}{36}$  = 2.25 mole of CH₄

Mole of CH₄ required = 225 × 10^-2

the nearest integer = 225

This is a multiple choice answer as classified in NCERT Exemplar

Option (D)

Explanation: Glycogen is a branched polymer of glucose found in the liver, muscles, and brain of animals.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A)

Explanation: Semi-synthetic polymers are obtained from natural polymers. Cellulose derivatives like cellulose nitrate, cellulose acetate rubber are examples of semi-synthetic polymers.

Cis-polyisoprene is not a semi-synthetic polymer while other examples are semi-synthetic polymer.

This is a multiple choice answer as classified in NCERT Exemplar

Option (B)

Explanation: Polyacrylonitrile is used as a wool substitute in the manufacture of commercial fibers such as orlon or acrilan.

This is a multiple choice answer as classified in NCERT Exemplar

Option (C)

Explanation: PHBV (Poly beta-hydroxybutyrate co-beta-hydroxy valerate) is a biodegradable polymer. It undergoes bacterial degradation in the environment. The structure is shown as,

This is a multiple choice answer as classified in NCERT Exemplar

Option (A)

Explanation: Dacron or Terylene is formed by the condensation polymerization of ethylene glycol and phthalic acid with the elimination of water molecules. The structure of Terylene is,

This is a multiple choice answer as classified in NCERT Exemplar

Option (B)

Explanation: Low-density polythene is obtained from the polymerization of ethane under high pressure and temperature. Low-density polyethylene is tough, a poor conductor of electricity and has a highly branched structure.

Low-density polythene is not hard because branched structure prevents stacking and thus, reduces the intermolecular force of attraction.

So, option (B) is correct.

This is a multiple choice answer as classified in NCERT Exemplar

Option (D)

Explanation: The given structure is caprolactam. Nylon-6 is prepared from the monomer caprolactam. It is obtained by heating caprolactam with water at a high temperature.

This is a multiple choice answer as classified in NCERT Exemplar

Option (B) and (C)

Explanation: Buna-S and neoprene are the polymers that needs at least one diene monomeric unit. Buna- S is a polymer formed from the polymerization of 1,3-butadiene and styrene. While, Neoprene is formed by the polymerisation of chloroprene.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A) and (C)

Explanation: Thermosetting polymers are cross linked polymers. These polymers on heating undergo cross linking in moulds. They become infusible on heating so cannot be reused again.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A) and (D)

Explanation: Thermoplastic polymers are linear or slight branched-chain polymers. This type of polymer softens on heating and hardens on cooling. For example, Teflon and polystyrene are thermoplastic polymers.

So, options (A) and (D) are correct.

This is a multiple choice answer as classified in NCERT Exemplar

Option (C) and (D)

Explanation: Fibers are thread-forming solids. They possess high tensile strength and high modulus. They have strong intermolecular forces of attraction like hydrogen bonding. Nylon and Terylene are used as fibers.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A) and (D)

Explanation: The formation of addition polymers is accomplished through the repeated addition of monomer molecules with double or triple bonds, such as polythene from ethene and polypropene from propene. Homopolymers are addition polymers formed by the polymerisation of a single monomeric species. 

This is a multiple choice answer as classified in NCERT Exemplar

Option (A) and (D)

Explanation: Condensation polymers are formed by the addition of more than one monomeric unit. Bakelite and Melamine formaldehyde resin are condensation polymers. Bakelite is a polymer formed from phenol and formaldehyde. Melamine formaldehyde resin is a polymer formed from melamine and formaldehyde.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A) and (B)

Explanation: The polymers that are not harmful to the environment are biodegradable polymers. PHBV (Poly beta-hydroxybutyrate co-beta-hydroxy valerate) is a biodegradable polymer. It undergoes bacterial degradation in the environment. PHBV is obtained by the polymerization of 3-hydroxybutyric acid and 3-hydroxypentanoic acid.

Nylon-2, Nylon-6 polymers are also biodegradable. It is obtained by the polymerization of glycine and aminocaproic acid.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A) and (C)

Explanation: Synthetic rubbers are either homopolymers or copolymers of 1,3-butadiene or its derivatives with another unsaturated monomer. Polychloroprene or neoprene and Buna-N are examples of synthetic rubber.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A) and (D)

Explanation: Polyamides: These polymers with amide linkages are important examples of synthetic fibers and are known as nylons.

Polyesters: These are the polycondensation products of dicarboxylic acids and diols.

Dacron or terylene is the most well-known example of a polyester.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A), (B) and (D)

Explanation: Polyacrylonitrile is formed by the addition polymerisation of acrylonitrile in the presence of a peroxide catalyst. Polyacrylonitrile is used as a wool substitute in the manufacture of commercial fibers such as orlon or acrilan.

Polystyrene has the monomer unit styrene.

Teflon is made by heating tetrafluoroethene at high pressures with a free radical or persulphate catalyst.

This is a multiple choice answer as classified in NCERT Exemplar

Option (A) and (D)

Explanation: Vulcanisation is a process used to improve the physical properties of natural rubber. This method involves heating a mixture of raw rubber, sulphur, and an appropriate additive to temperatures ranging from 373 K to 415 K. Sulphur forms cross links at the reactive sites of double bonds during vulcanisation, stiffening the rubber.

This is a short answer type question as classified in NCERT Exemplar

While manufacturing tyre rubber, 5 % sulfur is used as a crosslinking agent. A natural linear polymer of 2-methyl-1, 3-butadiene becomes hard on treatment with sulfur and forms vulcanised rubber. The structure of the product formed is,

This is a short answer type question as classified in NCERT Exemplar

Addition polymers formed by the polymerization of a single monomeric species are known as homopolymers. The above-given polymer is a homopolymer.

This is a short answer type question as classified in NCERT Exemplar

Addition polymers formed by the polymerization from two different monomers are co-polymers. The above-given polymer is a co-polymer. For example Buna-N, Buna-S.

This is a short answer type question as classified in NCERT Exemplar

This is a type of chain-growth polymerization. The molecules of the same monomer or different monomer are added together to form this type of polymer.

This is a short answer type question as classified in NCERT Exemplar

The polymer shown above is cross-linked or network polymer. They are formed from bi or tri-functional monomers that contain strong covalent bond between polymer chains.

This is a short answer type question as classified in NCERT Exemplar

The cis-polyisoprene molecule is made up of several chains that are held together by weak van there Waals interactions and has a coiled structure. Thus, it can be stretched like a spring and exhibits elastic properties.

This is a short answer type question as classified in NCERT Exemplar

Rubber is a natural polymer. It is also known as an elastomer due to its elastic properties. It is manufactured from rubber latex.

This is a short answer type question as classified in NCERT Exemplar

Enzymes are biocatalysts that are present in the body. They are basically proteins, and they are also considered as polymers.

This is a short answer type question as classified in NCERT Exemplar

Yes, nucleic acids, proteins, and starch can be considered step growth polymers because this type of polymerization involves a condensation reaction between two monomers. Loss of simple molecules such as water, alcohol results in this type of polymerization and it results in the formation of high molecular mass polymers.

This is a short answer type question as classified in NCERT Exemplar

Melamine formaldehyde polymer is formed by the condensation polymerization of melamine and formaldehyde.  This is resin intermediate.

This is a short answer type question as classified in NCERT Exemplar

A vulcanisation process is used to improve the physical properties of natural rubber. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between 373 K to 415 k. Sulphur forms cross links at the reactive sites of double bonds during vulcanization, stiffening the rubber.

This is a short answer type question as classified in NCERT Exemplar

Cis-polyisoprene has a coiled structure which consists of various chains held together by weak Van there Waals force of attraction. It can be stretched like a spring and thus, has elastic properties.

This is a short answer type question as classified in NCERT Exemplar

LDP: The polymerization of ethene under high pressure and temperature in the presence of peroxide catalyst gives low-density polythene. It is obtained through free radical addition and has a high branched structure. It is chemically inert and is a poor conductor of electricity. It is used for manufacturing toys, bottles.

HDP: When addition polymerization of ethene takes place in a hydrocarbon solvent in the presence of a catalyst such as triethylaluminium and Ziegler-Natta catalyst at high temperature and pressure then high-density polythene is formed. It consists of linear molecules. It is also chemically inert. It is used for manufacturing buckets, dustbins.

This is a short answer type question as classified in NCERT Exemplar

Free radicals are generated from benzoyl peroxide. Alkanes, dienes are polymerized in the presence of free radical inhibitors like benzoyl peroxide, acetyl peroxide. For example, benzoyl peroxide inhibitor is used for the polymerization of ethene to polythene. First, phenyl peroxide radicals are formed which are added to the double bond of ethene generating a new and larger free radical.

This is a short answer type question as classified in NCERT Exemplar

Polymers that possess amide linkage are termed as nylon. Fibers have a strong intermolecular force of attraction like hydrogen bonding. It leads to the close packing of the structure which imparts the crystalline nature.

This is a short answer type question as classified in NCERT Exemplar

Urea-formaldehyde resin is used in laminated sheets. The monomer involved in the formation of urea formaldehyde resin is urea and formaldehyde.

This is a short answer type question as classified in NCERT Exemplar

Proteins have some similar structural similarities with synthetic polyamides. Proteins and polyamides both contain amide linkage.

This is a short answer type question as classified in NCERT Exemplar

Monomers used in addition to polymerization through free radical pathway should be very pure because even the traces of impurities acts like inhibitors. It leads to the formation of polymers with a shorter chain lengths.

This is a matching answer type question as classified in NCERT Exemplar

(i) → (e) (ii) → (c) (iii) → (a) (iv) → (b) (v) → (d)

This is a matching answer type question as classified in NCERT Exemplar

(i) → (c) (ii) → (a) (iii) → (b) (iv) → (e) (v) → (d)

This is a matching answer type question as classified in NCERT Exemplar

(i) → (b) (ii) → (c) (iii) → (a) (iv) → (e) (v) → (d)

This is a matching answer type question as classified in NCERT Exemplar

(i) → (d) (ii) → (e) (iii) → (a) (iv) → (f) (v) → (b) (vi) → (c)

This is a matching answer type question as classified in NCERT Exemplar

(i) → (d) (ii) → (a) (iii) → (b)

This is a matching answer type question as classified in NCERT Exemplar

(i) → (b) (ii) → (d) (iii) → (a) (iv) → (d) (v) → (c)

This is a matching answer type question as classified in NCERT Exemplar

(i) → (f) (ii) → (e) (iii) → (a) (iv) → (c) (v) → (b) (vi) → (d)

This is a matching answer type question as classified in NCERT Exemplar

(i) → (d) (ii) → (a) (iii) → (b) (iv) → (e) (v) → (c)

This is a assertion and reason answer type question as classified in NCERT Exemplar

(ii) Assertion and reason both are correct statements and reason explains the assertion.

Explanation:  Rayon is a semi synthetic polymer. It is preferred over cotton fabric because its properties are improved by acetylation.

This is a assertion and reason answer type question as classified in NCERT Exemplar

(iv) Assertion is correct statement and reason is wrong statement. (v) Assertion is wrong statement and reason is correct statement.

Explanation:  Most of the Synthetic polymers are not biodegradable. A large number of the polymers are resistant to the degradation process of the environment and therefore, are responsible for the accumlation of polymeric solid waste material.

This is a assertion and reason answer type question as classified in NCERT Exemplar

(i) Assertion and reason both are correct statement but reason does not explain assertion.

Explanation: Olefinic monomers undergo addition polymerisation. The molecules of the same monomer or different monomer are added together to form this type of polymer. This mode of polymerisation leads to an increase in chain length.

This is a assertion and reason answer type question as classified in NCERT Exemplar

(ii) Assertion and reason both are correct statements and reason explains the assertion.

Explanation: Polyamides are best used as fibres because of high tensile strength. They have the strongest intermolecular forces of attraction like hydrogen bonding. It lead to close packing of chains and increase the crystalline character.

This is a assertion and reason answer type question as classified in NCERT Exemplar

(v) Assertion is wrong statement and reason is correct statement.

Explanation: Synthetic rubber is a type of rubber polymer that are capable of getting stretched to twice of its length. They are homopolymers of either 1,3-butadiene derivatives or copolymers of butadiene. Polychloroprene or neoprene is a type of synthetic rubber.

This is a assertion and reason answer type question as classified in NCERT Exemplar

(i) Assertion and reason both are correct statements but reason does not explain assertion.

Explanation: Thermosetting polymers are cross linked polymers. They are highly branched polymers with high molecular masses. These polymers on heating undergo cross linking in moulds. They become infusible on heating.

This is a assertion and reason answer type question as classified in NCERT Exemplar

(iv) Assertion is correct statement and reason is wrong statement. (v) Assertion is wrong statement and reason is correct statement.

Explanation:  Most of the Synthetic polymers are not biodegradable. A large number of the polymers are resistant to the degradation process of the environment and therefore, are responsible for the accumlation of polymeric solid waste material.