| Date | May 2019 | Marks available | 1 | Reference code | 19M.3.sl.TZ2.5 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Identify | Question number | 5 | Adapted from | N/A |
Question
Polymers have a wide variety of uses but their disposal can be problematic.
Draw a section of isotactic polychloroethene (polyvinylchloride, PVC) showing all the atoms and all the bonds of four monomer units.
The infrared (IR) spectrum of polyethene is given.
Suggest how the IR spectrum of polychloroethene would differ, using section 26 of the data booklet.
Identify a hazardous product of the incineration of polychloroethene.
Explain how plasticizers affect the properties of plastics.
Suggest why the addition of plasticizers is controversial.
Markscheme
correct bonding [✔]
Cl atoms all on same side and alternate [✔]
Note: Continuation bonds must be shown.
Award [1 max] if less than or more than four units shown.
Accept a stereo formula with all atoms and bonds shown.
«strong additional» absorption at 600–800 «cm–1» [✔]
Any one of:
HCl [✔]
Cl2 [✔]
dioxins [✔]
C [✔]
CO [✔]
Any two of:
embedded/fit between chains of polymers [✔]
prevent chains from forming crystalline regions [✔]
keep polymer strands/chains/molecules separated/apart [✔]
increase space/volume between chains [✔]
weaken intermolecular/dipole-dipole/London/dispersion/instantaneous dipoleinduced dipole/van der Waals/vdW forces «between chains» [✔]
increase flexibility/durability/softness [✔]
make polymers less brittle [✔]
leach into foodstuffs/environment
OR
«unknown» health/environmental consequences [✔]
Note: Accept “plasticizers cannot be recycled”.
Examiners report
Quite a few candidates scored at least one mark although most either scored both or none for this polymer structure.
Almost all students who attempted this question received the mark for identifying the correct absorption band.
This was a well answered question, with most candidates identifying at least one method plasticizers affect the properties of plastic.
Many students received a mark for this question although some did not because their answers were too vague.
Syllabus sections
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18M.3.sl.TZ2.4b.i:
State the chemical reason why plastics do not degrade easily.
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19M.3.sl.TZ1.4c(ii):
The trace quantities of dioxins from tyre fires are rarely inhaled and instead settle on the ground.
Describe why this is a health concern.
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19M.3.sl.TZ2.5e:
Suggest why the addition of plasticizers is controversial.
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19M.3.hl.TZ2.5d:
Suggest why the addition of plasticizers is controversial.
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17N.3.sl.TZ0.7b.ii:
One of the two infrared (IR) spectra is that of polyethene and the other of polytetrafluoroethene (PTFE).
Deduce, with a reason, which spectrum is that of PTFE. Infrared data is given in section 26 of the data booklet.
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17N.3.sl.TZ0.7c:
Many plastics used to be incinerated. Deduce an equation for the complete combustion of two repeating units of PVC, (–C2H3Cl–)2.
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18N.3.sl.TZ0.2d:
Repeating units of several polymers are listed.
The infrared (IR) spectrum of one of these polymers is shown.
Deduce, giving a reason, the name of this polymer and its Resin Identification Code (RIC), using sections 26 and 30 in the data booklet.
- 19N.3.hl.TZ0.5c: Discuss why the recycling of plastics is an energy intensive process.
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18N.3.sl.TZ0.2b.ii:
In an incomplete combustion of the polyvinyl chloride, PVC, it was found that hydrogen chloride, carbon monoxide, carbon dioxide, and water vapour were released.
Formulate an equation for this reaction using the formula of the PVC repeating unit.
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18M.3.sl.TZ1.4d:
Suggest two of the major obstacles, other than collection and economic factors, which have to be overcome in plastic recycling.
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18M.3.sl.TZ2.4b.ii:
Compare two ways in which recycling differs from reusing plastics.
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19M.3.hl.TZ1.4c:
Tyre fires emit trace quantities of polychlorinated dibenzofurans and polychlorinated dibenzo-p-dioxin.
Outline, using section 31 of the data booklet, why polychlorinated dibenzofuran is not classed chemically as a dioxin but considered “dioxin-like”.
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19M.3.sl.TZ1.4c(i):
Tyre fires emit trace quantities of polychlorinated dibenzofurans and polychlorinated dibenzo-p-dioxin.
Outline, using section 31 of the data booklet, why polychlorinated dibenzofuran is not classed chemically as a dioxin but considered “dioxin-like”.
