When aqueous ammonia is added to CuSO_4 solution, the solution turns deep blue due to the formation of tetramine copper (II) complex. [Cu(H_2O)_6]^(2+)(aq)+4NH_3(aq) leftrightarrow[Cu(NH_3)_4]^(2+)(aq) among H_2O and NH_3 which is stronger lewis base.

When aqueous ammonia is added to CuSO_4 solution, the solution turns d

1.	When aqueous ammonia is added to CuSO_4 solution, the solution turns deep blue due to the formation of tetramine copper (II) complex. [Cu(H_2O)_6]^(2+)(aq)+4NH_3(aq) leftrightarrow[Cu(NH_3)_4]^(2+)(aq) among H_2O and NH_3 which is stronger lewis base.
Answer» Solution :Copper (II) sulphate solution , for example contains the blue hexaaqua copper (II) complex ion. IN the first stage of the reaction, the ammonia acts as a Bronsted-Lowrybase. With a small amount of ammonia solution, hydrogen ions are pulled off two water molecules in the hexaaqua ion. This PRODUCES a neutral complex, one carrying no charge. If you remove two positively charged hydrogen ions from a 2+ ion, then obviously there isn.t GOING to be any charge left on the ion. Because of the lack of charge, the neutral complex isn.t soluble in water and so you get a pale blue precipitate. `[CU(H_2O)_6]^(2+)+2NH_3 leftrightarrow [Cu(H_2O)_4OH]+2NH_4^+` This precipitate is often WRITTEN as `Cu(OH)_2` and called copper (II) hydroxide. The reaction is reversible because ammonia is only a weak base. That precipitate dissolves if you add an EXCESS of ammonia solution, giving a deep blue solution. the ammonia replaces four of the water molecules around the copper to give tetramine diaqua copper (II) ions. The ammonia uses it lone pair to form a coordinate covalent bond with the copper. It is acting as an electron pair donor-a lewis base. `[Cu(H_2O)_4]^(2+)+4NH_3to[Cu(NH_3)_4(H_2O)_2]^(2+) +H_2O`