# Question #b01a3

##### 1 Answer
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 $A {l}^{3 +}$ ions and $C {l}^{-}$ ions:

$A {l}_{2} C {l}_{6} + 12 {H}_{2} O \rightarrow 2 {\left[A l {\left({H}_{2} O\right)}_{6}\right]}^{3 +} + 6 C {l}^{-}$

The small, highly charged $A {l}^{3 +}$ weakens the $O - H$ bonds resulting in a hydrolysis reaction:

${\left[A l {\left({H}_{2} O\right)}_{6}\right]}^{3 +}$ $+ {H}_{2} O \rightarrow {\left[A l {\left({H}_{2} O\right)}_{5} O H\right]}^{2 +} + {H}_{3} {O}^{+}$

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.