Question
Do you expect different products in solution when aluminium (III) chloride and potassium chloride are treated separately with:
(i) normal water (ii) acidifed water and (iii) alkaline water?
Solution
| Potassium chloride (KCl) | Aluminium (III) chloride (AlCl3) |
1. Normal water. KCl being a salt of strong base and strong acid does not undergo hydrolysis in normal water but simply dissociates to give K+ (aq) and Cl- (aq) ions.  |
1. Normal water. AlCl3 being a salt of weak base and strong acid, it undergoes hydrolysis in normal water. |
| 2. Acidified water and alkaline water. Since aqueous solution of KCl is neutral, therefore in acidified water and alkaline water, the ions will remain as such i.e. do not react further. | 2. In acidic water. H+ ions react with Al(OH)3 to form Al3+ (aq) ions and H2O. Hence in acidic water, AlCl3 exists as Al3+(aq) and Cl-(aq) ions.  |
3. In alkaline water.  reacts to form soluble tetrahydroxaluminate complex or meta-aluminate ion.  |
