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Iron3-thiocyanate Equilibrium

Does anyone know what happens to Iron3-thiocyanate under different conditions, such as heating, cooling and adding Fe(NO3)3?  I think after adding Fe(NO3)3 it would become darker red because of the added Fe, but I am not completely sure. Heat should speed up a reaction and ice should decrease, I think.

kingchemist Tue, 11/03/2009 - 14:10

It's an equilibrium and the position of the equilibrium can be changed

Fe3+(aq) + SCN-(aq) Fe(NCS)2+(aq)
  paler                                darker

So adding more Fe3+ will push the equilibrium to the right as the forward reaction is favoured. (Use Le Chatelier's principle to help predict what happens)

I suspect that the reaction is exothermic from left to right as bonds are being made. (bond making is exothermic while bond breaking is endothermic)

Fe3+(aq) + SCN-(aq) Fe(NCS)2+(aq)  + heat  (making bonds releases energy)
  paler                                darker

So raising the temperature will favour the endothermic direction and the mixture becomes paler.
Lowering the temperature will favour the exothermic direction and the equilibrium shifts to the right (becomes darker)