Addition Polymerisation — Structured Questions (Cambridge International A-Level Chemistry): Exam Questions

Polymer X can be formed from an alkene. The structure of polymer X is shown in Fig. 1.1.

Fig. 1.1

State the type of polymerisation involved in the formation of polymer X.

Extract:

Polymer X can be formed from an alkene. The structure of polymer X is shown in Fig. 1.1.

{align=center} Fig. 1.1

i) Draw the fully displayed formula of the monomer used to form polymer X.

ii) State the name of polymer X.

State two reasons why the disposal of poly(alkenes) such as polymer X is difficult.

Butene, C₄H₈, can exist as three isomers.

Isomer A is a position isomer of isomers B and C and does not show geometric isomerism.

Isomers B and C are geometric isomers of each other.

Isomer B is the cis isomer.

Isomer C is the trans isomer.

i) Draw the displayed formulae of the three isomers, A, B and C, of butene, C₄H₈.

ii) State the names of all three isomers, A, B and C, of butene, C₄H₈.

Extract:

Butene, C4H8, can exist as three isomers.

Isomer A is a position isomer of isomers B and C and does not show geometric isomerism.

Isomers B and C are geometric isomers of each other.

Isomer B is the cis isomer.

Isomer C is the trans isomer.

Isomer A = but-1-ene (4-carbon chain with C=C at C1)

Draw the displayed formula of the addition polymer formed by isomer A.

Extract:

Butene, C4H8, can exist as three isomers.

Isomer A is a position isomer of isomers B and C and does not show geometric isomerism.

Isomers B and C are geometric isomers of each other.

Isomer B is the cis isomer.

Isomer C is the trans isomer.

A student was asked to draw the displayed formula of the addition polymer of isomers B and C. They suggested that there were two structures as shown in Fig. 2.1.

Fig. 2.1

State why the student's two suggested structures are the same addition polymer.

A molecule of chloroethene is shown in Fig. 3.1.

Fig. 3.1

Chloroethene can be polymerised to form poly(chloroethene).

State the alternative name for poly(chloroethene).

Extract:

A molecule of chloroethene is shown in Fig. 3.1.

Chloroethene can be polymerised to form poly(chloroethene).

Draw a diagram of the structure of poly(chloroethene) including three repeat units.

State a problem caused by the combustion of poly(chloroethene) as a method of disposal and suggest how the effects of this problem can be reduced.

Addition polymers are made by the polymerisation of alkenes.

Explain what is meant by the term addition polymerisation.

Trans-hept-2-ene can be made into an addition polymer.

i) Draw the displayed formula of trans-hept-2-ene.

ii) Draw the structure of poly(hept-2-ene) showing two repeat units.

Extract:

Trans-hept-2-ene can be made into an addition polymer.

i) Draw the displayed formula of trans-hept-2-ene.

ii) Draw the structure of poly(hept-2-ene) showing two repeat units.

Suggest why the polymer made from trans-hept-2-ene is not called poly(trans-hept-2-ene).

Trans-hept-2-ene is a liquid at room temperature and pressure but poly(hept-2-ene) is a solid.

Explain why there is a difference in the states of trans-hept-2-ene and poly(hept-2-ene).

Polyvinyl chloride (PVC) is a polymer which is rigid enough for use as a drainpipe and flexible enough for plastic aprons.

State the IUPAC name of PVC.

Fig. 2.1 below shows a section of the PVC polymer.

Fig. 2.1

i) Draw the repeating unit of PVC.

ii) Draw the structure and state the name of the monomer of the PVC polymer.

iii) Construct the equation to represent the formation of PVC from its monomer.

The polymer poly(propene) is formed from the monomer propene.

i) Draw the repeating unit of this polymer.

ii) The properties of two different polymers, poly(methylpropene) and poly(ethene) are compared to each other. Complete Table 2.1 by placing an X in the correct box. You may place more than one X for each physical property.

Table 2.1

iii) Explain why the melting point of poly(methylpropene) is much higher than that of methylpropene.

Polymers are unreactive compounds due to their long non-polar chain of saturated carbon-carbon and carbon-hydrogen bonds. This means that they are safe to use, but it also means that they are non-biodegradable as they are not attacked by biological agents such as enzymes.

Table 2.2 shows three different ways in which polymers can be disposed of.

Table 2.2

State the disadvantage of each method of disposal to complete Table 2.2.

Poly(tetrafluoroethene), also known as PTFE, is an addition polymer used as a non-stick coating in pans as it is very unreactive.

Draw the displayed formula of the monomer used to form PTFE.

Draw two repeating units of poly(tetrafluoroethene).

The table shows the melting points of two polymers.

Explain the differences in melting point of these two polymers in terms of the intermolecular forces between the chains.

Poly(ethene) bags pollute the environment for a long time because they are non-biodegradable.

Describe two pollution problems that are caused by non-biodegradable polymers.

The structures of two different polymers, poly(ethene) and poly(propene) are shown in Fig. 4.1.

Fig. 4.1

Suggest two reasons why these polymers are unreactive.

State one advantage and one disadvantage of the unreactivity of addition polymers.

Another example of a polymer is polystyrene which is often used as packing material and electrical insulation.

Fig. 4.2 shows three repeating units of the polymer.

Fig. 4.2

Draw the structure of monomer X which is used to form the polymer shown in Fig. 4.2.

Extract:

Another example of a polymer is polystyrene which is often used as packing material and electrical insulation.

Fig. 4.2 shows three repeating units of the polymer.

Draw the structure of monomer X which is used to form the polymer shown in Fig. 4.2.

The structure of monomer X is: phenylethene (a C=C double bond with a phenyl ring attached to one carbon)

Two different monomers can also join together to form an addition polymer.

Monomer X can react with monomer Y to form a polymer. Two repeating units of this polymer are shown in Fig. 4.3.

Fig. 4.3

i) Draw the structure of monomer Y which reacts with monomer X to form the polymer shown in Fig. 4.3.

ii) State the IUPAC name of monomer Y.

Poly(but-1-ene) is insoluble in water so is used in applications such as making water pipes.

Write an equation to show how poly(but-1-ene) is formed from the monomer but-1-ene.

Not all polymers are insoluble in water. One example is poly(vinyl alcohol) known as PVA. PVA is used in applications such as in the casing of detergent-filled capsules.

A section of the polymer chain of PVA is shown in Fig. 5.1.

Fig. 5.1

i) Draw the structure and state the IUPAC name of the monomer of PVA.

ii) Suggest why PVA is soluble, but poly(but-1-ene) is not.

Combustion can be used to dispose of poly(alkenes), such as poly(but-1-ene).

State one advantage and one disadvantage to the environment of disposing of polymers by combustion.

Poly(chloroethene), PVC, can also be disposed of via combustion but it produces toxic waste gases including hydrogen chloride.

Suggest a reagent that can be used to remove this toxic gas from the waste gases.

Poly(methyl methacrylate) is used as a glass substitute in Perspex.

A section of the polymer chain is shown in Fig. 1.1.

Fig. 1.1

Draw the skeletal formula of the monomer.

Explain why poly(methyl methacrylate) is fairly unreactive.

Bioplastics, such as biodegradable plastics, offer a sustainable alternative to oil-based products.

Where the use of plant-based polymers is not possible, photodegradable polymers are being developed.

i) Explain how photodegradable polymers are broken down.

ii) Suggest two disadvantages of using photodegradable polymers.

Explain how p-orbitals are involved in the formation of the C=C bond in chloroalkenes.

You should include a sketch in your answer.

Compound Y has six possible structural isomers of C₃H₃Cl₃.

Two of these isomers are shown in Fig. 2.1.

Fig. 2.1

i) State the IUPAC name of isomer 1.

ii) Draw three other structural isomers of C₃H₃Cl₃ that are chloroalkenes.

iii) Show two repeat units for the polymer formed by isomer 2.

Polymers can be disposed of by incineration.

i) Write a balanced symbol equation for the incineration of poly(chloroethene). Carbon dioxide, water and HCl are formed.

ii) State the environmental impact of the carbon dioxide produced during this reaction.

iii) State the environmental impact of the hydrogen chloride produced during this reaction.

iv) Suggest how the environmental impact of the hydrogen chloride could be reduced.

But-2-ene, CH₃CH=CHCH₃, is an important compound which is obtained from the cracking of hydrocarbons present in crude oil.

Some reactions of but-2-ene are shown in Fig. 3.1.

Fig. 3.1

State the structural formulae of the organic compounds A to C.

Extract:

But-2-ene, CH3CH=CHCH3, is an important compound which is obtained from the cracking of hydrocarbons present in crude oil.

But-2-ene can be polymerised to give poly(but-2-ene). Draw the structural formula of a portion of the polymer chain in poly(but-2-ene) showing two repeat units.

State two reasons why there is an increasing demand for polymers to be recycled rather than incinerated.