IB Questionbank

User interface language: English | Español

Date	November 2018	Marks available	1	Reference code	18N.3.sl.TZ0.4
Level	SL	Paper	3	Time zone	TZ0
Command term	Describe	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.

[2]

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.

[1]

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.

[2]

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

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

oxidation state of C in CNTs is higher than in C₆H₁₂/cyclohexane

loss of H’s/hydrogens ✔

«oxidation at» anode/positive/+ «electrode» ✔

Accept “oxidation number” for “oxidation state”.

Examiners report

[N/A]

Syllabus sections

Options » A: Materials » A.4 Liquid crystals

Options » A: Materials

Options

Question

Markscheme

Examiners report

Syllabus sections

View options