Describe what you observe when the Fe3+ is added to the solution in the petri dish.

What chemical species must have been formed to account for your observation?

What chemical species did the Fe3+, that was added to the solution in the petri dish, react with to produce the change you observed?

 

The two petri dishes contain approximately equal amounts of the original mixture prepared by mixing the Fe3+(aq) and SCN-(aq) solutions. We identified the product of the reaction FeSCN2+(aq).

When we add Fe3+(aq) to the solution in the petri dish on the left we observe the solution gets darker. This is very interesting. Adding some Fe3+(aq) causes the solution to get darker, it appears that adding the Fe3+(aq) causes more FeSCN2+(aq) to be formed.

We could understand this to suggest that in the solution in the petri dish on the left there must have been some SCN-(aq). So when I added Fe3+(aq) there was a reaction to produce more of the product, FeSCN2+(aq).

So the original beaker containing the solution of FeSCN2+(aq) must also have some SCN-(aq) present.