Question

1. What will happen if I add water to a FeSCN+2 solution?

FeSCN+2(aq) + H2O(l) <--> ????


2. Will the equilibrium shift to the left or right?

The FeCNS⁺⁺ is red colored. I think adding water will simply dilute the red color.

Won't it react in any way?



Small highly charged cations, such as Fe⁺⁺⁺ do hydrolyze with water to form the hexaaquo complex and they in turn can react with water molecules to form H3O⁺ and the corresponding Fe(OH)(H2O)⁺⁺. But in this case, the CNS^- is such a strong complexing agent with Fe(III) that I discounted that. The iron(III)thiocyate complexs I have seen just become less intensely colored; although, I never tested one with litmus paper. If the aquo complex will form it will have been there from the initial time the CNS simplex is formed. Since these complexes are formed in aqueous solutions, anyway, there is only a few ppm of the complex there and mole after mole of water, so adding more water to a solution that is already 99.99% water can't make much difference one way or the other.

and the corresponding Fe(OH)(H2O)++.
<b>I made a typo here. It should have read Fe(OH)(H2O)₅⁺⁺.

The reaction is
Fe(H2O)₆³⁺ + H2O <==> Fe(OH)(H2O)₅⁺⁺ and it has a hydrolysis constant just as say acetate or CN^- have. </b>