When aluminium metal or aluminium hydroxide is treated with hydrochloric acid, aluminium trichloride is formed. The reaction mixture is evaporated to obtain hydrated aluminium chloride.
2Al + 6HCl → 2AlCl3 + 3H2
Al(OH)3 + 3HCl → AlCl3 + 3H2O
Aluminium chloride is obtained by heating a mixture of alumina and coke in a current of chlorine.
Al2O3 +3C + 3Cl2 → 2AlCl3 + 3CO2
On industrial scale it is prepared by chlorinating aluminium around 1000 K
Anhydrous aluminium chloride is a colourless, hygroscopic substance.
An aqueous solution of aluminium chloride is acidic in nature. It also produces hydrogen chloride fumes in moist air.
AlCl3 + 3H2O → Al(OH)3 + 3HCl
With ammonium hydroxide it forms aluminium hydroxide.
AlCl3 + 3NH4OH → Al(OH)3 + 3NH4Cl
With excess of sodium hydroxide it produces metal aluminate
AlCl3 + 4NaOH → NaAlO2 + 2H2O + 3NaCl
It behaves like a Lewis acid and forms addition compounds with ammonia, phosphine and carbonylchloride etc... Eg. AlCl3.6NH3.
· Anhydrous aluminium chloride is used as a catalyst in Friedels Crafts reactions
· It is used for the manufacture of petrol by cracking the mineral oils.
· It is used as a catalyst in the manufacture on dyes, drugs and perfumes.
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