Abstract:

Electrochemistry is one of the most difficult parts of chemistry for the first year students. At different levels, especially at introductory level, students have common misconceptions in electrochemistry. It has been observed that students have difficulty in producing scientifically accepted electrochemical cell diagrams (shorthand notations for the cell) and predicting the spontaneous cell reactions. In Daniel-Jacobi cell or in shorthand notation for this cell students forget that in reality not molar concentration, but activity, i.e. effective concentration which is function of concentration, which depends on the nature of the materials and ionic strength of solutions, is indicated.

In literature an exact model of Daniel-Jacobi cell, active metal/inactive metal Zn/Cu, is often used for explanation of galvanic cell. Cu and Zn electrodes often immersed in sulphates solutions of the same metals. Only in some textbooks Zn/Cu electrodes are immersed in solutions of nitrates. But ionic strength of copper and zinc sulphates and nitrates are different. Regardless of the applied solutions of salts (sulphate, nitrate or other) in Daniel-Jacobi cell it is necessary to indicate activity in shorthand notation of Daniel-Jacobi cell.

Students need to understand that in practice there may be other varieties of Daniel-Jacobi cell. In particular, other pairs of metal electrodes active metal/active metal (Fe/Ni) or a pair of the metal inactive/inactive metal (Cu/Ag and Ag/Pb or Cu/Fe) have been described. In this article question “Are there any example of Daniel-Jacobi cell, where a pair of electrodes is made of very active metals?” has been answered by the student response which used Mg/Al electrode pair. The expected cathode reaction is not reduction of Al ions, but hydrogen or oxygen depolarization reaction in acidic medium or one of several reduction reactions of nitrate ions.

The article investigates the way to improve the knowledge of students and conceptual difficulties in understanding basic aspects of electrochemistry related to galvanic cells. In order to avoid misunderstanding in electrochemistry, the method of electromotive force (EMF) calculation of galvanic cells and their classification into various types have been proposed.

Keywords:

electrochemistry, galvanic cell, electromotive force