Anhydride alcl3is covalent while alcl3.6h2o is ionic in nature

in anh. alcl3 , the al ions are small and have high +ve charge (+3) , this ion have high polarising power and hence polarises cl^-1 ion strongly , due to high polarisation of cl ^-1 ion by al ^ 3 + ion the covalent charecter is produced in alcl3 . 
hybrid salt is alcl3 . 6h20 , which will be obtained by dissolving anh . alcl3 in h20 , 
in this a large hydration energy is released , this ionisation energy helps in ionisation of hydrated salt . HOPE IT CLEARS 
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