When cobalt(II) chloride is added to pure water, the Co2+ ions hydrate. The hydrated form then reacts with the Cl- ions to set up the equilibrium shown below.

Co(H2O)62+ + 4 Cl-CoCl42- + 6 H2O

(pink) (Blue)

Which statement describes the change that the system will undergo if hydrochloric acid is added?

a.) It should become more blue.

b.) It should become more pink.

c.) The equilibrium will shift to the right.

d.) The equilibrium will shift to the left.

e.) Two of these.

Two of these.

Explanation:

Considering this reaction:

Co(H2O)62+ + 4 Cl-CoCl42- + 6 H2O, the equilibrium could shift either to the left or to the right depending on the concentration of the two competing ligands, Cl- and H2O. If the concentration of water is increased and the solution becomes more dilute, the equilibrium shifts to the left and the solution becomes more pink. If the concentration of the Cl- is increased by adding more HCl, the equilibrium shifts towards the right and the solution becomes more blue.

Hence the two answers among the options given are;

It should become more blue and the equilibrium will shift to the right.