Question #b01a3

1 Answer
Michael
Oct 5, 2015

The 1st case involves hydrolysis. The 2nd case is just dilution so is not really a reaction.

Explanation:

Aluminium chloride is a white solid which reacts vigorously with water to give hydrated #Al^(3+)# ions and #Cl^-# ions:

#Al_2Cl_6+12H_2Orarr2[Al(H_2O)_(6)]^(3+)+6Cl^(-)#

The small, highly charged #Al^(3+)# weakens the #O-H# bonds resulting in a hydrolysis reaction:

#[Al(H_2O)_(6)]^(3+) # #+H_2Orarr[Al(H_2O)_(5)OH]^(2+)+H_3O^(+)#

The resulting solution is, therefore, quite acidic.

Hydrated aluminium chloride cannot exist as a solid for this reason so adding water to its solution will simply dilute it.

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