Open Site - Science: Chemistry: Electrochemistry

Top: Science: Chemistry: Electrochemistry

Overview

Electrochemistry deals with the relationship of electricity to chemical changes and with the interconversion of chemical and electrical energy.

Anode

The electrode where oxidation occurs in an electrochemical cell. It is the positive electrode in an electrolytic cell, while it is the negative electrode in a galvanic cell. The current on the anode is considered a positive current according to international convention; however, in electroanalytical chemistry the anodic current is often considered negative. Contrast with cathode.

Cathode

The electrode where reduction occurs in an electrochemical cell. It is the negative electrode in an electrolytic cell, while it is the positive electrode in a galvanic cell. The current on the cathode is considered a negative current according to international convention; however, in electroanalytical chemistry the cathodic current is often considered positive. Contrast with anode.

Calomel electrode

A commonly used reference electrode. It is very similar to the silver/silver-chloride electrode both in construction and in theory of operation. The silver metal is replaced by mercury (electrical connection is made by an inert metal wire), the salt is mercury chloride, and the solution is saturated potassium chloride. Abbreviated as "SCE," for: "saturated calomel electrode." The equilibrium electrode potential is a function of the chloride concentration of the internal electrolyte ("filling solution"). The electrolyte is practically always saturated potassium chloride (hence the name: "saturated calomel electrode," SCE, "calomel" is an old name for mercurous chloride), producing a potential of 0.244 volt against the standard hydrogen electrode at 25 C.