Synthetic polymers (Edexcel IGCSE Chemistry)

The following molecule can undergo addition polymerisation.

What is the correct repeat unit?

Poly(chloroethene) is a polymer.

It is made from its monomer, chloroethene.

Chloroethene has the percentage composition by mass

C = 38.4%      H = 4.8%      Cl = 56.8%

Show, by calculation, that the empirical formula of chloroethene is C₂H₃Cl

The molecular formula of chloroethene is also C₂H₃Cl

Chloroethene can be prepared by a two‐stage process.

In stage 1, ethene reacts with chlorine in the presence of an iron(III) chloride catalyst to form dichloromethane.

The reaction is exothermic.

C₂H₄ + Cl₂ → C₂H₄Cl₂

i) Give the formula of iron(III) chloride.

(1)

ii) State the purpose of using a catalyst.

(1)

iii) State the meaning of the term exothermic.

(1)

iv) What type of reaction occurs in stage 1 between ethene and chlorine?

(1)

v) In stage 2, dichloroethane decomposes into chloroethene and hydrogen chloride. Give a chemical equation for this reaction.

(1)

i) Draw the displayed formula of

• chloroethene

• the repeat unit of poly(chloroethene)

(3)

ii) Draw a dot‐and‐cross diagram to represent a molecule of chloroethene. Show only the outer electrons of each atom.

(2)

This question is about alkenes and polymers.

Ethene (C₂H₄) can be represented by different types of formula.

i) Complete the table by giving the missing information.

(2)

ii) Ethene is a member of the homologous series of alkenes. All members of the same homologous series have the same general formula. Give two other characteristics of a homologous series.

(2)

1. ............................................................................
2. ............................................................................

Ethene is used to make poly(ethene).

 i) State the type of polymerisation used to form poly(ethene).

(1)

ii) Complete the equation for the polymerisation of ethene.

(2)

iii) Poly(ethene) is used to make plastic bags. Corn starch from plants can also be used to make polymers for plastic bags. The table gives some information about poly(ethene) and polymers made from corn starch.

Use the information in the table and your knowledge to discuss the advantages and disadvantages of using poly(ethene) to make plastic bags.

(5)

The diagram shows the repeat unit of another polymer.

Draw the displayed formula of the monomer used to make this polymer.

Polyesters can be made by condensation polymerisation. Ethanediol can react with butanedioic acid (a carboxylic acid containing two -COOH groups) to make a polymer.

Which of the following is a correct repeat unit for this polymer?

Poly(propene) is an example of a polymer. The structure of a poly(propene) molecule is shown in below.

This polymer is made from a monomer. Draw the structure of the monomer molecule showing all covalent bonds.

A layer of poly(chloroethene) (PVC) is used to surround the copper in electrical cables.

Suggest why poly(chloroethene) is a suitable material for this purpose.

Some polymers are polyesters. What type of reaction takes place when polyesters are formed?

The repeating unit in a polyester molecule is shown below.

i) This polymer is made from two different monomers. Draw a molecule of each monomer showing all covalent bonds.

(2)

ii) Give the name or formula of the small molecule formed when the monomer molecules react to form an ester link.

(1)

i) Organic compounds can exist as isomers.

Explain what is meant by the term isomers.

(2)

ii) Organic compound Q reacts with bromine, without the presence of ultraviolet radiation, to form the compound C₄H₈Br₂.

Draw the displayed formulae of two isomers of Q.

(2)

An acrylic polymer can be formed from molecules with this structure.

i) A student describes the molecule as an unsaturated hydrocarbon.

Explain whether this is a correct description.

(2)

ii) Name the type of polymerisation that occurs in the formation of the polymer.

(1)

iii) Complete the equation for the polymerisation reaction.

 (2)

Octane is a compound in petrol.

The equation for the complete combustion of octane is

C₈H₁₈ + 12.5O₂ → 8CO₂ + 9H₂O

i) The fuel tank of a car contains 50.0 dm³ of octane.

Calculate the mass, in kg, of carbon dioxide formed if all the octane in the fuel

tank undergoes complete combustion.

[mass of 1 dm³ of octane = 700 g]

mass = ................................................kg

(5)

ii) State an environmental problem caused by carbon dioxide.

(1)

Polymers can be classified as addition polymers or condensation polymers.

An addition polymer can be formed from the monomer CH₂=CHCl

i) Name this monomer.

(1)

ii) Name the addition polymer formed from this monomer.

(1)

The diagram shows the repeat unit of a different addition polymer.

Draw the displayed formula of the monomer used to make this polymer.

Polyesters are condensation polymers.

The structures of two monomers that are used to make a polyester are:

i) Draw the structure of the repeat unit of the polyester formed from these two monomers.

(2)

ii) Identify the small molecule formed when these two monomers form the polyester.

(1)

Ethene can be used as a starting point in the manufacture of poly(chloroethene).

Stage 1 involves the formation of 1,2-dichloroethane and can happen by two different methods. 

• Both methods form 1,2-dichloroethane

• Method 1 involves the reaction of chlorine with ethene.

• Method 2 reacts ethene with hydrogen chloride and oxygen and forms a second product. 

Use chemical equations to compare the two methods.

Stage 2 in the manufacture of poly(chloroethene) from ethene involves the thermal decomposition of 1,2-dichloroethane. Stage 3 involves the polymerisation of the stage 2 product to form poly(chloroethene).

 i) Draw the displayed formula of the organic product of stage 2.

(2)

 ii) Describe the organic product of stage 2.

 (2)

Stage 3 involves the formation of poly(chloroethene). 

State the type of polymerisation that occurs in stage 3.

Two ways of disposing of polymers such as poly(chloroethene) are: 

• burying them in landfill sites

• burning them to release heat energy

Discuss the environmental problems caused by these two methods of disposal.

Polymerisation is the reaction of monomer molecules to form polymer chains.

The diagram shows the formation of a polyester.

Explain why this is classed as a condensation reaction. 

Condensation polymers are commonly formed by the esterification reaction of a diol monomer and a dicarboxylic acid monomer. 

The repeat unit of a polyester is

Give the displayed formula of each of the two monomers needed to form this polyester.

The structures of two organic compounds that react together to form a polymer are shown. 

Give the repeat unit of the polymer formed.

State one advantage of biopolyesters.

The homologous series of alkenes can be converted into polymers.

i) Draw the displayed formulae of the first two members of the homologous series of alkenes.

 (2)

 ii) Use your answer to part (ii) to explain why these compounds are in the same homologous series.

 (3)

The diagram shows a range of organic compounds with the general formula C₄H₈.

Identify the compounds that cannot form polymers. Explain your answer.

Compound D can be polymerised to form the polymer poly(2-methylpropene). 

Complete the equation for this polymerisation reaction. 

The diagram shows the repeat unit of the polymer formed by compound E.

 i) Give the empirical formula of the polymer.

 (1)

 ii) Identify another compound from part (b) that can form this polymer.

 (1)