In the extraction of aluminium by electrolysis, why is it necessary to dissolve aluminium oxide in molten cryolite?
A.
to reduce the very high melting point of the electrolyte
B.
cryolite is a base; aluminium oxide is amphoteric
C.
cryolite reacts with the aluminium oxide to form ions
D.
molten aluminium oxide alone would not conduct electricity
Exam No：9701_w13_qp_13 Year：2013 Question No：2
Answer:
A
Knowledge points:
6.1.1 calculate oxidation numbers of elements in compounds and ions
6.1.2 use changes in oxidation numbers to help balance chemical equations
6.1.3 explain and use the terms redox, oxidation, reduction and disproportionation in terms of electron transfer and changes in oxidation number
6.1.4 explain and use the terms oxidising agent and reducing agent
6.1.5 use a Roman numeral to indicate the magnitude of the oxidation number of an element
Solution:
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