An aqueous solution of #"AlCl"_3# is a product of the the neutralization reaction between hydrochloric acid (#"HCl"#) and aluminum hydroxide ( #"Al(OH)"_3#).
#"HCl"# is a strong acid, and #"Al(OH)"_3# is a weak base. When a strong acid solution and a weak base solution mix, the resulting saline solution will be slightly acidic, as the acid is stronger and "overpowers" the effects of the weak base, essentially.