Question

Zn2+ and Al3+ are amphoteric. Demonstrate

Answer 1

Explanation:

1) Amphoteric substances can react both like an acid or a base depending if they are in presence of a base or an acid.

Zinc hydroxide (Zn(OH)2):

In acid: $Zn(OH)_2 + 2 HCl \longrightarrow ZnCl_2 + 2 H_2O$

In base: $Zn(OH)_2 + 2 NaOH \longrightarrow Na_2[Zn(OH)_4]$

Aluminium hydroxide (Al(OH)3)

In acid: $Al(OH)_3 + 3 HCl \longrightarrow AlCl_3 + 3 H_2O$

In base: $Al(OH)_3 + NaOH \longrightarrow Na[Al(OH)_4]$

2) Reactions

a) $2 NH_3 + Cu^{2+} + 2 H_2O \longrightarrow 2 NH_4^+ + Cu(OH)_2$

$3 NH_3 + Fe^{3+} + 3 H_2O \longrightarrow 3 NH_4^+ + Fe(OH)_3$

b) $2 NH_3 + Zn^{2+} + 2 H_2O \longrightarrow 2 NH_4^+ + Zn(OH)_2$

$3 NH_3 + Al^{3+} + 3 H_2O \longrightarrow 3 NH_4^+ + Al(OH)_3$