[cye1]

question:
Co2+ (aq) + 2Cl- (aq) <---> CoCl2
pink                                    blue

So if you start with a pink solution, I know that if you add HCl (aq), the reaction turns from a pink to blue because the H+ and Cl- ions dissociate and the and the Cl- ions from the HCl (aq) bonds with the Co2+ (aq) in the original equation to make more blue CoCl2. 
Also, I know that if you add AgNO3 to this solution, you get a white precipitate because the Ag+ ions and Cl- ions bond to form the precipitate-->you're removing the Cl- ions, basically.

Why does adding water drive the reaction back to a pink solution? Is it because the O^2- ions bond with the Co2+ to form more pink? OK, I honestly have no idea.  HELP PLEASE!!!

Thanks!

[nj_bartel]

There's no reaction.  Adding water increases the dilution of the reactants.

[azmanam]

If you meant why does adding SILVER NITRATE drive the reaction back to pink, then consult LeChatlier's principle.

O(2-) is not a major reactant in any reaction involving water.  It just doesn't form under standard reaction conditions.

[cye1]

There's no reaction.  Adding water increases the dilution of the reactants.

ok...so if you dilute the reaction, why does it turn from blue back to pink? :/

[nj_bartel]

Think of it like this.  If you dump those two reactants in a lake, are they going to shift toward the products?

[cye1]

Think of it like this.  If you dump those two reactants in a lake, are they going to shift toward the products?

interesting...but why? especially when the reaction is reversible?

[Borek]

Pink Co²⁺ is in fact a complex with water, when you add Cl^- some of the water molecules are replaced with chloride ions. Would you expect concentration of this chloride containing complex to grow or to lower in diluted solution with excess water at hand?