Question

Aluminum ion in solution reacts with water to form aqueous hexaaguaaluminum ()ion. Write this reaction below, remember phases. Aluminum is more likely to form a hydrated complex than the other four ions remaining in solution, because of its relatively small size and high charge To separate the Group B2 ion, the solution first is made basic by adding ammonia. In the presence of this weak base the pH is adjusted to 9-10 and the group B ions form insoluble hydroxides. Aluminum and iron ions present in the solution as complex ions form white aluminum hydroxide and red-brown iron () hydroxide. Write the two reactions of hydroxide reacting with aluminum to make its hydroxide ppt and a separate equation for iron reacting with hydroxide to make its hydroxide ppt. Include phases Both hydroxides are insoluble in ammonia solution because neither iron nor aluminum forms a complex ion with ammonia. The copper ion in solution from Group D forms an aqueous dark blue copper (I) tetraamine complex ion [Cu(NHal2. Write this reaction with phases After centrifuging the reaction mixture, we decant the supernatant liquid containing the potassium, Cu(NH3]2, and calcium into a separate container. Then separate the two cations in the precipitate by adding sodium hydroxide. The aluminum hydroxide ppt dissolves, forming aqueous, colorless tetrahydroxoaluminate ion [Al(OH)]. Write this reaction with phases The iron hydroxide is not soluble in sodium hydroxide because it doesn't form a complex ion

Answer 1

The formation of hexaaquaaluminium(III) ion can be represented as follows

Al³⁺ (aq) + 6 H₂O (l) [Al(H₂O)₆]³⁺ (aq)

Addition of ammonia base into the water results in the availability of large amounts of OH^- ions, Both Al(III) ions and Fe(III) ions present in the water reacts with this hydroxide ions (OH^-) to form their respective hydroxides.

Al³⁺ (aq) + 3 OH^- (aq) Al(OH)₃ (s)

Fe³⁺ (aq) + 3 OH^- (aq) Fe(OH)₃ (s)

Group D metal ion Copper reacts in ammonia solution to form its tetraamine complex in the following way

Cu²⁺ (aq) + 4 NH₃ (aq) [Cu(NH₃)₄]²⁺ (aq)

After the addition of sodium hydroxide, the precipitate aluminium hydroxide reacts with the hydroxide ions to form aqueous tetrahydroxoaluminate ion

Al(OH)₃ (s) + OH^- (aq) [Al(OH)₄]^- (aq)