The pBlock Elements - Result Question 5

####6. Aluminium is extracted from alumina (Al2O3) by electrolysis of a molten mixture of: [2012]

(a) Al2O3+HF+NaAlF4

(b) Al2O3+CaF2+NaAlF4

(c) Al2O3+Na3AlF6+CaF2

(d) Al2O3+KF+Na3AlF6

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Solution:

  1. (c) Fused alumina (Al2O3) is a bad conductor of electricity. Therefore, cryolite (Na3AlF6) and fluorspar (CaF2) 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.


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