A student adds the following stresses one at a time to separate samples of an equilibrium mixture of [Co(H2O)6]^2+ (pink) <-> [CoCl4]^2- (blue) + 6 H2O (delta H > 0 forward) and records color change: Trial A: heat the solution -> turns blue Trial B: add concentrated HCl -> turns blue Trial C: add AgNO3 -> turns pink Trial D: add water -> turns pink
Why does adding water cause the solution to turn pink (Trial D)?
- Acheck_circle
Diluting Cl- (the reactant) shifts equilibrium back toward [Co(H2O)6]^2+
- B
Water removes heat from the reaction
- C
Water is a product, so adding water shifts forward
- D
AgNO3 forms with water
Explanation
Adding solvent reduces ion concentrations; the equilibrium shifts toward the side with more dissolved ions and less water on the right. Net effect: shift toward pink [Co(H2O)6]^2+.