How does ammonia react with a solution of `Cu^(2+)`?

Explanation

`NH_(3)` acts as a Lewis base. It donates its electron pair and forms a linkage with metal ion.
`underset("Bule")(Cu_((aq))^(2+)) + 4 NH_((aq))^(3) harr underset("Deep bule") ([Cu(NH_(3))_(4)]_((aq))^(2+))`