which of the following coordination compounds will most likely form a precipitate when treated with an aquesous solution of silver(l) nitrate?

A) [Cr(NH3)2CL3]
B) [Cr(NH3)6]Cl3
C) [Cr(NH3)Cl]SO4
D) Na3[Cr(CN)6]
E) Na[CrCl6]

i think its either a or b but i don't know which exactly is right?

Pick the one in which the Cl is not part of the coordination sphere with Cr.

that would be choice B right?

right. If the Cl is coordinated, it is a covalent bond and the covalent bonds doesn't allow the pptn of AgCl easily. Sometimes one can see a light cloudy color but not much. Outside the coordination sphere it is an ionic compound and the Ag^+ + Cl^- ==> AgCl proceeds easily.

That is correct! Choice B, [Cr(NH3)6]Cl3, is the most likely to form a precipitate when treated with an aqueous solution of silver(1) nitrate. In this compound, the chloride ion (Cl) is not part of the coordination sphere with chromium (Cr). Therefore, the chloride ion exists outside of the coordination complex as an ionic compound. When silver nitrate is added, the silver ion (Ag+) reacts with the chloride ion to form a precipitate of silver chloride (AgCl).

In choices A, C, D, and E, the chloride ion is coordinated with the chromium ion in the coordination complex. This results in a covalent bond and makes it less likely for a precipitate to form. While a light cloudy color may be observed in some cases, the precipitation of AgCl is not as readily facilitated as in choice B.