posted by PreMed33 on .
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?
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.