Predict feasibility of the reaction between Fe3+ and I-
We will discuss predicting feasibility of redox reaction between Fe3+ and. I- by using standard reduction potential.
Standard reduction potential is a measure of electron gaining power of an electrode. It may be positive or negative.
Positive electrode potential shows that the species is oxidising agent which can pull electrons from another regents. For the redox reaction to be possible, oxidising agent should be more powerful, it means it should be positive.
Among Fe3+ and I-, the oxidation number of Fe3+ is high and hence it is an Oxidising agent
Fe3+ +e = Fe2+ E0 = +0.77 v
I- = I2 + 2e E0 = -0.54 v
Since Fe3+ has higher potential, that is enough to pull electrons from iodide ion. So, the reaction is feasible.