Question

Question #b01a3

Answer 1

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.