With a mixture containing metal cations Cu (+2 charge), Cr (+2 charge), and Fe (+3) charge, all of which are attached to a NO3 ion.
Adding a concentrated solution of NH4OH(aq) causes precipitation of Cr (2+) and Fe (2+) as insoluble hydroxides. The Cu (2+) remained in solution and forms the complex ion Cu(NH3)4 (+2 charge).
Write a balanced molecular equation for the Cu reaction.