Thermodynamics

Thermodynamics plays an important role in our understanding of electrochemical processes. It can tell us whether a given redox reaction is spontaneous and therefore whether it is able to provide useful electrical energy. Thermodynamics also describes how to add reduction potentials to determine the cell potential for a galvanic or electrolytic cell. It also permits us to add reduction potentials of two reductions to calculate the potential of a new, or even theoretical, reduction half-reaction. Thermodynamics provides further insight into electrochemical cells at non-standard conditions in its derivation of the Nernst Equation. The Nernst Equation allows us to calculate the cell potential at any conditions and suggests the construction of concentration cells such as pH meters or other ion-selective electrodes.

Combining ideas from thermodynamics, stoichiometry, and basic electrical theory makes this section the most important to understand if you wish to become proficient at doing electrochemistry problems. Such problems tend to be among the more difficult ones on any exam because they cut across many fields in chemistry and require deep analytical thought and an thorough understanding of electrochemical cells. In this section, you will get to know and love such formulae as DG^o = -nFE^o (useful for converting free energy and potentials) and E = E^o - (RT/nF) ln Q (the Nernst Equation).

Despite all that thermodynamics has to offer to electrochemistry, it's about as dry as burnt toast. It requires much algebra and clear logic. My advice to you as you read this section is not to be passive, but to actively question and to prove to yourself any assertions I may make. Question my proofs because in the argumentation rests a good deal of the knowledge I am trying to convey. Most of all, try to understand the big picture as well as how to do the presented problems.