Q2 / 160 · AP EAMCET 2020 (18 Sep Shift 2) · Chemistry

Which statement is incorrect regarding Hall-Heroult process for metallurgy of aluminium? 1. Use of \(\mathrm{Na}_3 \mathrm{AlF}_6\) lowers the melting point of \(\mathrm{Al}_2 \mathrm{O}_3\) 2. Steel vessel with lining of carbon acts as cathode. 3. Graphite is used as anode. 4. Carbon dioxide gas is generated at cathode.

  • A
    1
  • B
    2
  • C
    3
  • Correct answer
    D
    4

Solution

In Hall-Heroult process for extraction of aluminium (crude) from alumina \(\left(\mathrm{Al}_2 \mathrm{O}_3\right)\). Statements (1), (2) and (3) are correct because cryolite \(\left(\mathrm{Na}_3 \mathrm{AlF}_6\right)\) is added to \(\mathrm{Al}_2 \mathrm{O}_3\) to lower, its melting point. Here, steel vessel with lining of carbon acts as cathode and graphite acts as anode, but statement (4) is incorrect because \(\mathrm{Al}\) gets deposited at cathode.

Hence, the correct answer is option: 'D'.

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