The aqueous solution of AlCl3 contains Al3+ ions because

AlCl3+6H2O→AlH2O6Cl3≈AlH2O6+3 + 3Cl-In AlH2O6Cl3 the oxidation state of Al is +3 .Ionisation energy is absorbed energy for the removal of three electrons.Where as hydration energy is released energy during hydration of one mole of Al+3 ions.In the above reaction both the processess are involved but hydration energy is greater than that of ionisation energy.Hence removal of three electrons easily takes place and gives Al+3 ion in solution.