source : english.turk.cebilgi.com
Method of preparation of anhydrous aluminium chloride (Al2Cl6 or AlCl3)
1) By passing dry chlorine gas over heated aluminium :
anhydrous AlCl3 is obtained.
2Al + 3Cl2 ——-> 2AlCl3
2) By passing dry HCl in heated aluminium :
2Al + 6HCl ———-> 2AlCl3 + 3H2
3) By passing dry chlorine gas over heated alumina and coke :
Al2O3 +3C +3Cl2 ———> 2AlCl3 + 3CO
Methods of preparation of hydrated aluminium chloride:
1) By dissolving aluminium in hydro chloric acid :
2Al + 6HCl ——–> 2AlCl3 + 3H2
2) By dissolving aluminium hydroxide in HCl :
AlCl3 solution is obtained which on concentration gives crystals of AlCl3
Al(OH)3 + 3HCl ———-> AlCl3 + 3H2O
1) It is colourless, crystalline solid, soluble in water.
2) Hydrolysis :
Aqueous solution of AlCl3 is acidic in nature because on hydrolysis ,it gives strong acid.
AlCl3 + 3H2O———-> Al(OH)3 + 3HCl
3) Reaction with Sodium hydroxide (NaOH) :
AlCl3 + 3NaOH ———-> Al(OH)3 + 3NaCl
Al(OH)3 + NaOH ———–> NaAlO2 + H2O
4) Reaction with Ammonium hydroxide (NH4OH) :
White precipitate of aluminium hydroxide is obtained. This precipitate do not dissolve in excess of NH4OH
AlCl3 + 3NH4OH ———> Al(OH)3 + 3NH4Cl
5) Reaction with dry ammonia (NH3 gas) : Addition compound is obtained.
AlCl3 + 6NH3 ———-> AlCl3. 6NH3
6) Effect of heat :
On heating aluminium chloride decomposes to give Alumina, hydrochloride and water.
2AlCl3 . 6H2O ———-> Al2O3 + HCl + H2O
i) It is used as catalyst in friedel craft’s reaction.
ii) It is used as mordant in dye.
Structure of Aluminium chloride:
AlCl3 is electron deficient compound so it exists as dimer (Al2Cl6) .
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