Exercise 6 | Solubility and Precipitation Reactions

The formation of a solid precipitate and ammonium nitrate is observed when aqueous ammonia is added to a solution of copper(II) nitrate. However, the precipitate disappears when additional aqueous ammonia is added and a complex ion, [Cu(NH3)4]2+, is formed.


Write the balanced chemical equation for the two reactions.

Copper(II) nitrate: Cu(NO3)2

1st reaction:  Cu(NO3)2 (aq) + 2 NH3 (aq) + 2 H2O (l)  Cu(OH)2 (s) + 2 NH4NO3 (aq)

2nd reaction: Cu(OH)2 (s) + 4 NH3 (aq) → [Cu(NH3)4]2+ + 2 HO- (aq)