Entropy is one of the less discussed and analyzed among the state functions studied in the thermodynamics of electrochemical systems. Few universities and post-graduate Electrochemistry courses and textbooks deal with this function’s basic aspects. Consequently, the importance of its practical applications needs to be thoroughly studied. Entropy changes are related to the reversible heat released or absorbed in electrochemical reactions. This reversible heat is also named molar electrochemical Peltier heat, which phenomenologically differs from the conventional Peltier heat used in physics and thermoelectric theory. In a simple and detailed manner, this manuscript presents fundamental concepts plus practical and experimental aspects for quantifying entropy changes and the associated molar electrochemical Peltier heat effects in a reversible and isothermal half-cell electrochemical reaction.

The differences between the conventional and molar electrochemical Peltier heat are also presented. Electrochemistry professors can use the material included here to encourage university and post-graduate students to further their knowledge and understanding of the electrochemical processes.