Question 19M.3.sl.TZ2.5
| Date | May 2019 | Marks available | [Maximum mark: 7] | Reference code | 19M.3.sl.TZ2.5 |
| Level | sl | Paper | 3 | Time zone | TZ2 |
| Command term | Draw, Explain, Identify, Suggest | Question number | 5 | Adapted from | N/A |
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.
[2]
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.
Quite a few candidates scored at least one mark although most either scored both or none for this polymer structure.
The infrared (IR) spectrum of polyethene is given.
Suggest how the IR spectrum of polychloroethene would differ, using section 26 of the data booklet.
[1]
«strong additional» absorption at 600–800 «cm–1» [✔]
Almost all students who attempted this question received the mark for identifying the correct absorption band.
Identify a hazardous product of the incineration of polychloroethene.
[1]
Any one of:
HCl [✔]
Cl2 [✔]
dioxins [✔]
C [✔]
CO [✔]
This was a well answered question, with most candidates identifying at least one method plasticizers affect the properties of plastic.
Explain how plasticizers affect the properties of plastics.
[2]
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 [✔]
Many students received a mark for this question although some did not because their answers were too vague.
Suggest why the addition of plasticizers is controversial.
[1]
leach into foodstuffs/environment
OR
«unknown» health/environmental consequences [✔]
Note: Accept “plasticizers cannot be recycled”.