| Date | November 2018 | Marks available | 2 | Reference code | 18N.3.sl.TZ0.4 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Predict | Question number | 4 | Adapted from | N/A |
Question
While heating solid cholesteryl benzoate, Reinitzer discovered the liquid crystal phase.
Outline two observations that he could have made.
The structure of biphenyl nitrile is shown.
Describe, giving a reason, a feature of the molecular structure, other than its polarity, that allows biphenyl nitrile to show liquid crystal behaviour.
Arc discharge, consisting of two inert metal electrodes in a liquid solvent, is one method of producing carbon nanotubes (CNTs).
Predict, giving a reason, the electrode at which the solvent cyclohexane, C6H12, will decompose to form CNTs.
Markscheme
Any two of:
cloudy/foggy/hazy phase «at first melting point» ✔
clear liquid phase «at second melting point/higher temperature» ✔
two «different» melting points
OR
new phase observed over a wide temperature range ✔
Accept “exhibit both liquid and solid properties at the same time” for M3.
ALTERNATIVE 1:
«bulky/long» C5H11/R/alkyl «group/chain» AND prevents molecules from packing closer together «to form solid state» ✔
ALTERNATIVE 2:
biphenyl «fragment»/two benzene rings/two aromatic rings AND «makes molecule» rigid/rod-shaped ✔
Accept “rigid/rod-shaped molecule, so aligns with other molecules” for ALTERNATIVE 2.
«average» oxidation state of C in C6H12/cyclohexane = –2 AND in CNTs = 0
OR
oxidation state of C in CNTs is higher than in C6H12/cyclohexane
OR
loss of H’s/hydrogens ✔
«oxidation at» anode/positive/+ «electrode» ✔
Accept “oxidation number” for “oxidation state”.
Examiners report
Syllabus sections
-
17N.3.sl.TZ0.6a:
State equations for the formation of iron nanoparticles and carbon atoms from Fe(CO)5 in the HIPCO process.
- 17N.3.sl.TZ0.6c: Discuss one possible risk associated with the use of nanotechnology.
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19M.3.hl.TZ2.4e:
Carbon nanotubes are added to metals to increase tensile strength.
Write an equation for the formation of carbon nanotubes from carbon monoxide.
-
19M.3.sl.TZ1.6a:
Describe the structure and bonding of a carbon nanotube.
Structure:
Bonding:
-
19M.3.sl.TZ2.4e:
Carbon nanotubes are added to metals to increase tensile strength.
Write an equation for the formation of carbon nanotubes from carbon monoxide.
-
19M.3.hl.TZ1.6b:
Suggest one application for carbon nanotubes.
-
17M.3.sl.TZ1.8b:
Suggest why nanoparticles need to be handled with care.
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17M.3.sl.TZ1.8a:
State the major advantage that nanoparticles have in these applications.
- 17N.3.sl.TZ0.6b: Outline why the iron nanoparticle catalysts produced by the HIPCO process are more efficient...
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19N.3.sl.TZ0.3c:
Nanotubes are used to support the active material in nanocatalysts.
Explain why oxygen cannot be used for the chemical vapour deposition (CVD) preparation of carbon nanotubes.
-
18M.3.sl.TZ2.5a:
State the source of carbon for MWCNT produced by arc discharge and by CVD.
-
18M.3.sl.TZ1.3b.iii:
Describe how carbon nanotubes are produced by chemical vapour deposition (CVD).
-
16N.3.sl.TZ0.5b:
Nanocatalysts play an essential role in the manufacture of industrial chemicals.
(i) Describe the high pressure carbon monoxide (HIPCO) method for the production of carbon nanotubes.
(ii) Outline one benefit of using nanocatalysts compared to traditional catalysts in industry.
-
19M.3.sl.TZ1.6b:
Suggest one application for carbon nanotubes.
-
19M.3.hl.TZ1.6a:
Describe the structure and bonding of a carbon nanotube.
Structure:
Bonding:
-
18M.3.sl.TZ1.3b.ii:
State one physical property of HDPE that will be affected by the incorporation of carbon nanotubes.
- 20N.3.sl.TZ0.4a: Explain these properties of carbon nanotubes.
- 20N.3.hl.TZ0.4a: Explain these properties of carbon nanotubes.
