Using a simple cell to predict reaction feasibility

In this experiment we measure the electrode potential of the iron(II)-iron(III) electrode system and that of the iodine-iodide electrode system. We use a copper-copper(II) electrode system as a reference electrode because it is easier to use than the standard hydrogen electrode. By working out the cell e.m.f. for the iron(II)-iron(III) and iodine-iodide cell we can predict the feasibility for the reaction between iron(III) and iodide ions. Watch the video, and try to make such a prediction, checking your answer in the link below.

Video - to measure some electrode potentials

Predicting feasibility for this reaction

We now try to carry out the reaction in a test tube. We need to remember that even though we may predict a reaction as feasible on thermodynamic grounds we cannot tell anything about the rate of the reaction.

We test the starting materials and products using starch solution and potassium hexacyanoferrate(III) solution. Watch the video to discover the results, and try to write a balanced equation for the reaction. Check your answer using the link below.

Video - the reaction between iron(III) ions and iodide ions

Equation for the reaction and conclusions