MODULE 17

17.0 ELECTROCHEMISTRY INTRODUCTION

17.1 Review of Redox Chemistry

17.2 Galvanic Cells

17.3 Electrode and Cell Potentials

17.4 Potential, Free Energy and Equilibrium

17.5 Batteries and Fuel Cells

17.6 Corrosion

17.7 Electrolysis

17.8 Worksheets with Questions and Answers

17.0 ELECTROCHEMISTRY INTRODUCTION

Electrochemistry is the study of chemical properties and reactions that involve charged species (ions) in solution, and includes both electrolysis and electrochemical cells. Electrochemistry is best defined in the study of the interchange of chemical and electrical energy. It is primarily concerned with the two processes that involve oxidation-reduction reactions: the generation of an electric current from a spontaneous chemical reaction and, the possible processes, the use of a current to produce chemical charge.

Electrochemistry deals with chemical reactions that produce electricity and the changes associated with the passage of electrical current through matter. The reactions involve electron transfer, and so they are oxidation-reduction (or redox) reactions. Many metals may be purified or electroplated using electrochemical methods. Devices such as automobiles, smartphones, electronic tablets, watches, pacemakers, and many others use batteries for power. Batteries use chemical reactions that produce electricity spontaneously and that can be converted into useful work. All electrochemical systems involve the transfer of electrons in a reacting system. In many systems, the reactions occur in a region known as the cell, where the transfer of electrons occurs at electrodes.

Insert copper and zinc electrodes in a potato and they will react spontaneously. The potato, however, still feels cool to the touch, and the metal emits neither bright flashes nor a luminescent glow. Instead, a voltmeter shows energy in the form of moving electrons or electricity. We may also surmise that acids in the potato enable the metal to react spontaneously. We’ll explore that later in the chapter. 

Like light or heat, electricity is one more form of energy, and electrochemistry is the study of how reactions produce electric charge and current, as well as the study of how electricity can drive chemical processes.

Because moving electrons make electric current, electrochemistry  means electron transfer. Nearly all electrochemical reactions are paired oxidation-reduction processes, redox reactions for short. This is true whether a process powers a battery, lights up a diode, plates metals or breaks ionic bonds. Many electrochemical processes occur in an apparatus that includes a container, barriers, wires, and electrodes. This piece of equipment is called a cell (Image credit for potato battery: Eileen H. Kramer)