Correcting Frost Diagram Misconceptions Using Interactive Frost Diagrams

Frost diagrams provide convenient illustrations of the aqueous reduction potentials and thermodynamic tendencies of different oxidation states of an element. Undergraduate textbooks often describe the lowest point on a Frost diagram as the most stable oxidation state of the element, but this interpretation is incorrect because the thermodynamic stability of each oxidation state depends on the specific redox conditions in solution (i.e., the potential applied by the environment or an electrode). Further confusion is caused by the widespread use of different, contradictory conventions for labeling the y-axis of these diagrams as either nE° or −nE°, among other possibilities. To aid in discussing and correcting these common mistakes, we introduce a series of interactive Frost diagrams that illustrate the conditional dependence of the relative stabilities of each oxidation state of an element. We include instructor’s notes for using these interactive diagrams and a written activity for students to complete using these diagrams.