What happens if you add ammonia to a solution of Copper(II)ions?

Question

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Answer 1

Ammonia is a weak base and when dissolved in water the reaction below occurs.  ("NH4OH"/"ammonium hydroxide" has no separate existence)

NH3(g) + H2O <=> NH4+(aq) + OH-(aq)

The hydroxide ions will react with copper(II) as follows:

Cu2+(aq) + 2OH-(aq) --> Cu(OH)2(s) (a pale blue precipitate)

{strictly: [Cu(H2O)6]2+(aq) + 2OH-(aq) <=> [Cu(H2O)4(OH)2](s) + 2H2O(l)}

On addition of an excess of ammonia solution the following occurs.

Cu2+(aq) + 4NH3(aq) --> [Cu(NH3)4]2+(aq) (a dark blue solution)

{strictly: [Cu(H2O)4(OH)2](s) + 4NH3(aq) <=> [Cu(NH3)4(H2O)2]2+*(aq) + 2OH-(aq) + 2H2O(l)

*the tetramminediaquacopper(II) ion

Answer 2

You get a blue precipitate which re-dissolves to give a distinctive blue solution. This is used as a test for Copper(ii) ions.

Answer 3

If you add Copper (II) ions in aqueous Ammonia, then this will happen:

1. At first there will be precipitate of basic Copper hydroxide.

2 CuSO4 + 2 NH4OH = CuSO4.Cu(OH)2 + (NH4)2SO4

2. But if u add more ammonia to the solution then this ppt will turn into a deep blue solution named Tetramine Cupric Sulphate or it is also known as Schwetzer reagent.

CuSO4.Cu(OH)2 + (NH4)2SO4 + 6NH4OH = 2 [Cu(NH3)4]SO4+ 8H2O