What happens when aqueous ammonia reacts with copper (I) chloride in the absence of air?

Question

Here's the whole problem. I couldn't fit it all in the subject line..

What happens when aqueous ammonia reacts with copper (I) chloride in the absence of air? What happens when air is admitted to the copper (I) chloride-ammonia solution?

Answer 1

I have done this reaction before; it actually looks pretty neat.

When ammonia is added to the CuCl, it forms a complex ion.  Unlike CuCl, this complex is soluble in water:

CuCl(s) + 2NH3(aq) -----> [Cu(NH3)2]+(aq) + Cl-(aq)

This complex is colorless (no allowed d to d transitions, if you care).

However, copper(I) is not very stable to oxidation, and will readily oxidize to a copper(II) complex in the presence of oxygen (the ammonia on the reactant side assumes you added excess ammonia in the first step):

4[Cu(NH3)2]+(aq) + O2(g) + 8NH3(aq) + 2H2O(l) -----> 4[Cu(NH3)4] 2+(aq) + 4OH-(aq)

Unlike the previous complex, this one is a dark blue color, so a dramatic color change will be observed upon admission of air.