Question

Which of the following methods can be used for the preparation of anhydrous aluminium chloride?

• A. Heating $AlC{l}_3.6H_{2}O$
• B. Heating a mixture of alumina and coke in a current of dry chlorine
• C. Passing dry HCl gas over heated aluminium powder
• D. Passing dry chlorine over heated aluminium

Answer 1

Answer: (B), (C), (D)

Heating a mixture of alumina and coke in a current of dry chlorine
Passing dry HCl gas over heated aluminium powder
Passing dry chlorine over heated aluminium

Anhydrous aluminium chloride can be prepared by the following methods:
(B) Heating a mixture of alumina and coke in a current of dry chlorine.
$A{l}_2{O}_3+3C+3C{l}_2\to 2AlC{l}_3+3CO\uparrow$

(C) Passing dry HCl gas over heated aluminium powder.
$2Al+6HCl\to 2AlC{l}_3+3H_2$

(D) Passing dry chlorine over heated aluminium.
$2Al+3C{l}_2\to 2AlC{l}_3$

It can not be obtained by heating of $AlC{l}_3.6H_{2}O$, because $AlC{l}_3$ is covalent and hence when the water of crystallisation is evaporated, $AlC{l}_3$ will react with the water to form the hydroxide.