PolymersAQA A-Level Chemistry: Topic test

1. 1
   A fibre company makes nylon-6 by heating a single monomer, 6-aminohexanoic acid, H₂N(CH₂)₅COOH, at high temperature. The monomer molecules join end to end to form long chains.

   (a)

   What type of polymerisation is this?

   [1 mark]

   • ACondensation, with the loss of a small molecule at each link
   • BAddition, with no small molecule lost
   • CAddition, with the breaking of a C=C double bond in each monomer
   • DCondensation, with the loss of hydrogen gas at each link

   (b)

   Which linkage joins the monomer units in nylon-6?

   [1 mark]

   • AEster, –COO–
   • BEther, –O–
   • CAmide, –CONH–
   • DAmine, –NH–

   (c)

   Give the repeating unit of nylon-6 and name the functional group that links the repeating units.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A biodegradable surgical suture is made from a polyester formed from butanedioic acid, HOOC(CH₂)₂COOH, and ethane-1,2-diol, HOCH₂CH₂OH. After a wound has healed, the suture slowly breaks down inside the body in contact with water.

   (a)

   Which bond in the polymer chain is broken when the suture breaks down?

   [1 mark]

   • AA C–C bond in the (CH₂)₂ section
   • BThe C=O double bond of an ester group
   • CA C–H bond in the (CH₂)₂ section
   • DThe C–O single bond in an ester link, –COO–

   (b)

   Why can this polyester be hydrolysed, whereas poly(ethene) cannot?

   [1 mark]

   • APoly(ethene) has stronger London forces between its chains
   • BThe carbon atom of the ester group is δ+ and can be attacked by water, whereas poly(ethene) has only non-polar bonds
   • CPoly(ethene) has a much higher relative molecular mass
   • DWater cannot act as a nucleophile, so only enzymes can break the ester link

   (c)

   Name the two products formed by complete hydrolysis of this polyester under acidic conditions.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Nylon-6,10 is a polyamide used in toothbrush bristles and machine gears. It is made from decanedioic acid, HOOC(CH₂)₈COOH (Mᵣ = 202.0), and hexane-1,6-diamine, H₂N(CH₂)₆NH₂ (Mᵣ = 116.0), with elimination of water.

   (a)

   Give the repeating unit of nylon-6,10 and calculate its relative formula mass. The Mᵣ of water is 18.0.

   [3 marks]

   (b)

   Explain the nature of the intermolecular forces between chains of nylon-6,10 and why they make the polymer strong with a high melting point.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A farming cooperative needs a mulch film that will not leave plastic in the soil after harvest. It is comparing poly(propene) film with a polyester film made from hexanedioic acid, HOOC(CH₂)₄COOH, and butane-1,4-diol, HO(CH₂)₄OH. Used film is covered in soil.

   (a)

   Give the repeating unit of the polyester and explain, with reference to its bonding, why it is biodegradable whereas poly(propene) is not.

   [6 marks]

   (b)

   The cooperative has some poly(propene) film that is contaminated with soil. Evaluate the advantages and disadvantages of recycling it and of burning it with energy recovery.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A section of a polyamide chain is: –NH(CH₂)₄NHCO(CH₂)₆CO–NH(CH₂)₄NHCO(CH₂)₆CO–. A chemist is asked to identify the monomers it was made from and to explain its properties.

   (a)

   Which pair of monomers forms this polyamide?

   [1 mark]

   • AButane-1,4-diamine and hexanedioic acid
   • BButane-1,4-diamine and octanedioic acid
   • CButane-1,4-diol and octanedioic acid
   • DOctane-1,8-diamine and butanedioic acid

   (b)

   Which intermolecular force is strongest between neighbouring chains of this polymer?

   [1 mark]

   • ALondon forces between the CH₂ groups
   • BIonic bonds between the chains
   • CHydrogen bonds between C–H and C=O groups
   • DHydrogen bonds between N–H and C=O groups

   (c)

   Explain why this is a condensation polymer and calculate how many molecules of water are released when one polymer chain forms from 100 molecules of the diamine and 100 molecules of the dicarboxylic acid.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A biologist buries strips of two plastics in moist compost. One is a polyester made from pentanedioic acid, HOOC(CH₂)₃COOH, and propane-1,3-diol, HO(CH₂)₃OH. The other is poly(phenylethene). After one year the polyester strip has almost disappeared and the poly(phenylethene) strip is unchanged. The biologist then considers how to dispose of waste poly(phenylethene).

   (a)

   Which statement best explains the observation for the strips?

   [1 mark]

   • APoly(phenylethene) has a greater relative molecular mass than the polyester
   • BThe polyester is made from smaller monomers, which makes it dissolve in water
   • CThe polyester has polar ester links that can be hydrolysed, whereas poly(phenylethene) has a non-polar chain of C–C bonds
   • DPoly(phenylethene) has ester links that cannot be hydrolysed

   (b)

   Which disposal method for waste poly(phenylethene) can recover useful energy?

   [1 mark]

   • ABurning in an incinerator that generates electricity
   • BBurying in landfill
   • CMelting and remoulding into new products
   • DSpreading on soil to be broken down by microorganisms

   (c)

   Give the repeating unit of the polyester and name the type of link that holds the monomers together.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   Alanine, CH₃CH(NH₂)COOH, can polymerise by itself on heating to form a polymer whose chains contain repeating units of alanine. A student is asked to explain how the polymer is made and how it breaks down.

   (a)

   Draw the repeating unit of the polymer formed from alanine. Name the small molecule lost during polymerisation and state how many of these molecules are lost when one chain forms from 50 alanine molecules.

   [3 marks]

   (b)

   The polymer is warmed with aqueous acid and slowly breaks down. Explain why the amide links can be hydrolysed, name the product and explain why poly(ethene) would not break down in this way.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A start-up is developing a carrier bag from a polyester made from butanedioic acid, HOOC(CH₂)₂COOH, and butane-1,4-diol, HO(CH₂)₄OH. The company wants to replace bags made from poly(ethene).

   (a)

   Explain how the polyester is formed, giving its repeating unit, and compare the intermolecular forces between its chains with those between chains of poly(ethene).

   [6 marks]

   (b)

   Evaluate the use of the polyester bag compared with a poly(ethene) bag in terms of how each can be disposed of.

   [6 marks]

   Total for question 8: 12 marks

End of questions