Question

I had this on a test, not sure how to do it

Explain, using balanced chemical reactions with the smallest integer coefficients, why each of following occurs.
a. CuI2 (insoluble in pure water) dissolves readily in aqueous ammonia, HN3(aq)
b. AgBr (insoluble in pure water) dissolves readily in NaCN.

Answer 1

First, I need to correct your formula for ammonia. It is NH3.
The CuI2 dissolves in NH3, easily, because it forms the Cu(NH3)4^+2 complex ion. The AgBr dissolves in NaCN, easily, because of the formation of the Ag(CN)2^- complex ion. [AgBr will dissolve in NH3, too, with the formation of Ag(NH3)2^+1]

CuI2 + 4NH3 ==> Cu(NH3)4^+2 + 2I^-
AgBr + 2NaCN ==> Ag(CN)2^- + 2Na+ + Br^-