[Fry]

Why does AgCl redissolve on addition of dilute ammonia solution to this equilibrium..

AgNO3 + Cl-  <--> AgCl + NO3-

I know the ammonia will start its own equilibria with water and produce hydroxide ions.. I just dont see how this will cause the AgCl to redissolve 

[Borek]

Complex.

[Sev]

Ammonia reacts with Ag+.  This would drive your reaction to the left.

[Fry]

Thanks!

So. if the Cl was replaced with Br in the entire reaction is it true that you would need a concentrated ammonia solution to redissolve the AgBr because Br- has a higher affinity for Ag+ than NH3?

How else can this higher affinity be explained? in terms of the higher electron density cloud of bromine and its ability to better polarize?

[AWK]

This problem can be explained by two equilibriums in solution - solubility product and complex formation.