Question

Suppose you are studying coordination compounds of Co(II) with the ligand pyridine (py, C5H5N, molar mass=79.10). You isolate a crystalline compound, and because the only available anions are Cl- and NO3-, you hypothesize that the empirical formula of the coordination compound must be Cow(py)x(Cl)y(NO3)z.

Addition of AgNO3 to aqueous solutions of the complex results in a cloudy white precipitate, presumably AgCl. You dissolve 0.100 g of the complex in H2O and perform a precipitation titration with 0.0500 M AgNO3 as the titrant. Using an electrode that is sensitive to [Ag+], you reach the endpoint after 9.00 mL of titrant is added. How many grams of chloride ion were present in the 0.100g sample?

Answer 1

All of that extraneous information makes one think this is a tough problem. Not so.
mols Ag present = M x L = ?
grams = mols Ag x atomic mass Ag.
By the way you must assume with this that the Cl ion is not "within" the complex but outside the coordination sphere so that it acts as a Cl ion.