Complexometric titration and stoichiometry.

Assume you are studying coordination compounds of Co(II) with the ligand pyridine (py, C5H5N, MW = 79.10). You isolate a crystalline compound and since the only available ions are chloride and nitrate, you hypothesize the empirical formula of the coordination compound must be Co(II)w(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 0.1000 g of the complex in water and perform a precipitation titration with 0.0500 M AgNO3 at the titrant. Using an electrode that is sensive to [Ag+], you reach the endpoint after 9.00 mL of titrant are added. How numerous grams of chloride ion were present in the 0.1000-g sample?

a. 1.60 x 10-2
b. 1.77 x 10-3
c. 4.50 x 10-4
d. 5.00 x 10-3
e. 6.38 x 10-2