Describe what you observe when the F- is added to the original solution in the beaker.

Explain why the solution changes color.

 

based on the previous experiments we know there is some Fe3+(aq) in the solution. Adding F- reacts with the Fe3+(aq) in the solution.

But the solution becomes completely colorless! The only way this could happen is if the FeSCN2+(aq) breaks down into Fe3+(aq) and SCN-(aq).

FeSCN2+(aq) ---> Fe3+(aq) + SCN-(aq)

The F- then reacts with the Fe3+(aq) that is formed. Eventually all of the FeSCN2+(aq) breaks down and solution becomes colorless.