Purification And Characterisation Of Organic Compounds Question 162
Question: Aluminium is extracted from alumina $ (Al_2O_3) $ by electrolysis of a molten mixture of
Options:
A) $ Al_2O_3+HF+NaAlF_4 $
B) $ Al_2O_3+CaF_2+NaAlF_4 $
C) $ Al_2O_3+Na_3AlF_6+CaF_2 $
D) $ Al_2O_3+KF+Na_3AlF_6 $
Show Answer
Answer:
Correct Answer: C
Solution:
[c] Fused alumina $ (Al_2O_3) $ is a bad conductor of electricity.
Therefore, cryolite $ (Na_3AlF_6) $ and fluorspar $ (CaF_2) $ are added to purified alumina which not only make alumina a good conductor of electricity but also reduce the melting point of the mixture to around 1140K.
BETA
