Suppose You Are Studying Coordination Compounds of Co(II)with the Ligand

Multiple Choice

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 since the only available anions are Cl^- and NO₃^-,you hypothesize the empirical formula of the coordination compound must be Co_w(py) _x(Cl) _y(NO₃) _z.
-You analyze for pyridine (K_b is approximately 10^-9) by dissolving 0.1000 g of complex in 10 mL of H₂O and titrating with a 0.01 M HCl solution.Which of the following indicators should be used to detect the endpoint? (Assume that the initial concentration of pyridine is approximately 0.01 M. )

A) bromophenol blue,pH range of color change = 3.0-4.6
B) methyl red,pH range of color change = 4.8-6.0
C) bromothymol blue,pH range of color change = 6.0-7.6
D) thymol blue,pH range of color change = 8.0 -9.6
E) alizarin yellow,pH range of color change = 10.1-12.0