Question

1. A student extended the study of the cobalt ion equilibrium in Part V. When silver nitrate was added to a test tube containing a blue equilibrium mixture of [CoCl4]2-, a white precipitate formed and the solution turned pink. The student correctly concluded that the white precipitate was silver chloride (AgCl). Explain this result using Le Chatelier’s Principle, and include appropriate chemical reactions to support your explanation.

Answer 1

AgNO3 + CoCl4]2- --> white precipitate; pink solution

white preciptate = AGCl

note that

AgCl(s) <--> Ag+(aq) + Cl-(aq)

meaning, that the first solution (test tube) was high on Cl- ions in solution, therefore, when adding the AgNO3, that is Ag+ and NO3- ions, you will have:

Q = [Ag+][Cl-]

since Q >> Ksp of AgCl which is about 1.8*10^-10

you will expect the preciptiation of AGCl which is white

le chateliar states that the equilibrium shifts toward the other side (in this case, reactants, or solid Agcl)