DP Chemistry (last assessment 2024)

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Question 19N.3.sl.TZ0.b(ii)

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Date November 2019 Marks available [Maximum mark: 3] Reference code 19N.3.sl.TZ0.b(ii)
Level sl Paper 3 Time zone TZ0
Command term Deduce, Formulate Question number b(ii) Adapted from N/A
b(ii).
[Maximum mark: 3]
19N.3.sl.TZ0.b(ii)

Metals are extracted from their ores by various means.

Aluminium is produced by the electrolysis of alumina (aluminium oxide) dissolved in cryolite.

Write half-equations for the electrolysis of molten alumina using graphite electrodes, deducing the state symbols of the products.

Anode (positive electrode):

Cathode (negative electrode):

[3]

Markscheme

Anode (positive electrode):
2O2− → 4e− + O2(g)
OR
2O2− + C → 4e− + CO2 (g) ✔

NOTE: Award [1 max] for M1 and M2 if correct half-equations are given at the wrong electrodes OR if incorrect reversed half-equations are given at the correct electrodes.

 

Cathode (negative electrode):
Al3+ + 3e− → Al (l) ✔
O2 gas AND Al liquid ✔

NOTE: Only state symbols of products required, which might be written as (g) and (l) in half-equations. Ignore any incorrect or missing state symbols for reactants.

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