alleryCryolite is added to alumina in the Hall-Heroult cell to
ACoat the cathode with a thin layer of carbon
BRaise the melting point and slow the reaction
CProduce coloured aluminium for jewellery use
DLower the melting point and improve conductivity
Answer & Solution
Correct answer: D. Lower the melting point and improve conductivity
1. Pure alumina melts above 2000 deg C.
2. Adding cryolite (Na3AlF6) lowers the melt to about 950 deg C.
3. It also increases the electrical conductivity.
4. So option A is correct.
_Source: Selina Concise Chemistry Class 10, Ch 7 Metallurgy (Mistral OCR'd PDF), section on cryolite role_
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