Question

When a strong base is added to a solution of CuSO4, which is pale blue, a precipitate forms and the solution above the precipitate is colorless. When ammonia is then added, the precipitate dissolves and the solution turns a deep navy blue. Net equation?

When ammonia is then added, the precipitate dissolves and the solution turns a deep navy blue. What is the net chemical equation that describes this event?

Answer 1

`underbrace(CuSO_4(aq))_"blue coloured solution"+2HO^(-)rarrCu(OH)_2(s)darr +SO_4^(2-)`

Explanation:

`Cu(OH)_2(s)+4NH_3(aq) rarr [Cu(NH_3)_4]^(2+) + 2HO^-`

The tetra-ammine complex gives the deep blue colour...

Note that the pale blue solution on the left sits atop a white precipitate of copper hydroxides...the stability of the complex ion allows the copper ion to go back into solution....