Question

You are working with the following equilibrium system in which one chromium complex is blue and one chromium complex is purple. The system is at equilibrium and is currently blue.
Predict how the color will change if aqueous Ag+ ions are added. Ag+ reacts with NH3 to form a colorless silver-ammonia complex ion.


[Cr(H2O)6]3+ (aq) + 6 NH3 (aq) arrow
[Cr(NH3)6]3+ (aq) + 6 H2O (l)

Reactant side is blue and product side is purple


a. The solution will turn from blue to purple.
b. The solution will become a darker blue.
c.The solution will become a lighter blue.
d.The solution will not change colors.

Answer 1

The system is on the blue side. If we add Ag^+, it will form the Ag(NH3)^+ complex which will remove NH3 from the system and that will shift the equilibrium to the left. Of the answers listed, the most likely is d. Whether b is correct, or not, also, depends upon how blue the solution is at equilibrium. If the blue color is pronounced, however, the additional shift to the left will not be enough to notice a change in intensity of the blue color.