Electrode potential is the voltage of two electrodes in a cell, often measured in volts. Hydrogen is the standard reference with zero volts. Electrochemical processes and corrosion can be predicted by understanding electrode potential. The Nernst equation can be used to calculate electrode potential. Zinc, copper, iron, aluminum, and calcium are commonly used for electrodes. The process requires scientific and mathematical understanding.
Electrode potential is the combined potential of two electrodes undergoing reactions in a cell. Typically measured in volts, it can differ based on the substances the electrodes are made of. Hydrogen is often considered the standard, with a potential of zero volts, from which the reactions of other elements are compared. Electrochemical processes can be predicted by understanding the electrode potential of a material, as well as the chances of it corroding under particular circumstances. Also called electromotive force (EMF), this potential is usually measured using a galvanic cell, which consists of two chambers, each with an electrode and connected by a piece of paper called a salt bridge.
The electric current of a cell is typically measured by a voltmeter. There may be no current; the potential difference between the electrodes, in this case, is usually the same as the EMF of the entire cell. EMF is typically measured at a temperature of 77°F (about 25°C) and typical sea-level air pressure. These conditions are used to measure the standard electrode potential in a two half-cell configuration. A hydrogen electrode is typically on one side of this layout, while the potential of that on the other side is usually determined by experiment.
Once this default value is derived, it is possible to predict how a substance will react. Usually, the higher the negative value of the potential, the more likely the element is to dissolve in a solution. No reaction is often observed in non-reactive metals. These are usually placed at the bottom of a standard electrode potential table, which identifies the EMF of different types of elements. Elements are generally ranked according to their tendency to react, so those with a positive charge rank higher because they react more often than negatively charged substances.
Standard conditions are not always available, so a calculation called the Nernst equation can be used to determine the electrode potential. It takes into account the temperature, a gas constant, how many particles called electrons are transferred, and the concentration of ions. While hydrogen is the standard reference, elements often used for electrodes include zinc and copper, iron, aluminum or calcium.
The electrode potential of each of these elements is used to calculate the voltage of a galvanic cell. Sometimes a separate calculation of atomic half-reactions is used to derive the EMF as well. The process of determining electrode potential may therefore require an understanding of scientific as well as mathematical principles.
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