A student has a solution containing a mixture of metal cations: Cu+2, Cr+2, and Fe+3, each a solution with NO3- anion. Adding a concentrated solution of NH4OH(aq) caused the precipitation of Cr+2 and Fe+3 as insoluble hydroxides. The Cu+2 remained in solution and forms the complex ion Cu(NH3)4+2. Which balanced molecular equations represent each of these reactions?