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Although anhydrous aluminium chloride is covalent but its aqueous solution is ionic in nature. Why?

Aluminium forms  covalent compound with chloride because lonisation enthalpy of Al+3 is very high, chlorine is unable to convert  Al into Al+3 ions.(∆iH= +5137 kJ/mole).
However, when anhydrous AlCl3 (which is covalent in character)  is dissolved in water, it undergoes, hydration as follow :                          AI2CI6 + H2O  ---> 2[Al(H2O)6]+3 + Energy    
Hydration of anhydrous aIuminium chloride is highly exothermic in nature. The hydration enthalpy is more than ionisation enthalpy of aluminium.This hydration enthalpy removes all the three valence electrons of the aluminium leading to the formation of Al3+ .This AI3+ is hydrated with water. Thus in water Al exist as [Al(H2O)6]+3 . The three electrons of aluminium is accepted by CI of AlCl3. Thus hydrated AlCl3 is ionic in nature. 

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