Synthetic polymers (Edexcel IGCSE Science (Double Award) (Modular): Chemistry Unit 2): Exam Questions

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

[1]

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

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.

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)