Explain why the molten electrolyte also contains cryolite.

State a half-equation for the reaction at the negative electrode (cathode).

Oxygen is produced at the positive electrode (anode). State the name of another gas produced at this electrode.

State two properties of aluminium that make it suitable for use as an overhead electric cable.

Alloys of aluminium with nickel are used to make engine parts. Explain, by referring to the structure of these alloys, why they are less malleable than pure aluminium.

it lowers the operating temperature/melting point (of alumina) / it saves heat/energy / improves conductivity / acts as a solvent;

Do not accept lowers melting point of aluminium.

Do not accept “lowers boiling point”.

\({\text{Al(l}}{{\text{)}}^{3 + }} + {\text{3}}{{\text{e}}^ - } \to {\text{Al (l)}}\);

Ignore state symbols.

Accept e instead of e^–.

carbon dioxide / carbon monoxide / fluorine / tetrafluoromethane;

Do not accept formulas since the name is asked for specifically.

high/good (electrical) conductivity and low density;

Do not accept lighter.

Accept malleable/ductile/resistant to (further) corrosion as one property.

Reference to high/good conductivity or low density needed.

in alloy different sized/Ni atoms/ions/particles disrupt regular structure;

stops layers from slipping/sliding / OWTTE;

Do not accept “stop layers moving”.

Accept diagrams if explanation clear.

This was reasonably well answered. However a surprising number of candidates were unable to write the half equation for reaction at the negative electrode in (a) (ii), and few candidates were able to give an explanation of the reduced malleability of the alloys in terms of their structure in b (ii).

This was reasonably well answered. However a surprising number of candidates were unable to write the half equation for reaction at the negative electrode in (a) (ii), and few candidates were able to give an explanation of the reduced malleability of the alloys in terms of their structure in b (ii).

This was reasonably well answered. However a surprising number of candidates were unable to write the half equation for reaction at the negative electrode in (a) (ii), and few candidates were able to give an explanation of the reduced malleability of the alloys in terms of their structure in b (ii).

This was reasonably well answered. However a surprising number of candidates were unable to write the half equation for reaction at the negative electrode in (a) (ii), and few candidates were able to give an explanation of the reduced malleability of the alloys in terms of their structure in b (ii).

This was reasonably well answered. However a surprising number of candidates were unable to write the half equation for reaction at the negative electrode in (a) (ii), and few candidates were able to give an explanation of the reduced malleability of the alloys in terms of their structure in b (ii).