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Electrolysis is an electrochemical process by which electrical energy is
used to promote chemical reactions that occur at electrodes. The anode
involves the oxidation process where species lose electrons which are
deposited at the anode. Gaining of electrons occurs at the Cathode. An
electrolytic cell is a non-spontaneous electrochemical system. The cell
potential of all electrolytic cells will be less than zero which will
result in a non-spontaneous system. Since delta G = - n F Ecell, a negative
cell potential would make delta G positive and therefore indicative of a
Electrolysis often involves metals that are capable of being reduced at the
Cathode to metallic atoms. These atoms can then be deposited on whatever is
serving as the cathode surface. This special kind of electrolysis is known
as electroplating, and it is the usual process for producing jewelry that
is silver, chromium, platinum, or gold plated objects. Copper plating
usually involves a Copper salt that serves as an electrolyte. The
electrolyte is a solution that allows electrical current to move through
the solution. This is essential to any electrolytic process.
Other substances besides metals can undergo electroysis. Water can ne
electrolyzed producing Hydrogen gas at the Cathode and Oxygen gas at the
anode at a ratio of two volumes of Hydrogen for every one volume of Oxygen
gas. Bauxite (Aluminum ore, Al2O3) can be electrolyzed to form Aluminum.
Before this industrial process was worked out, Aluminum cost per pound was
very high. As a result, few items were made from Aluminum which resists
corrosion better than Ferrous materials. After the electrolytic industrial
processing of Aluminum from Bauxite was worked out, Aluminum cost plummeted
to pennies per pound. Now virtually any item can be "galvanized" with
Aluminum coating. Aluminum is extremely light compared to Ferrous materials
and other metals.
The electrolytic process was investigated by Michael Faraday who worked out
the so called Laws of Electrolysis. Faraday discovered that "the amount of
deposition on an electrode is directly proportional to the current passing
through the electrolytic cell. One faraday of current (96,500 coulombs) of
current will deposit one gram equivalent mass of a substance. Two faradays
of current will deposit two gram equivalent masses of substance and so on.
A gram equivalent mass of a substance is equal to the Formula Mass of the
substance divided by the number of moles of electrons passing through a
cell. For example, if Cu+2 ion is reduced at a Cathode according to the
following half reaction:
Cu+2 + 2e- ------> Cu
Then the gram eq. mass of Cu is:
Atomic mass of Cu / 2 = 31.75 grams/ eq. mass
So if one faraday of current is passed through the electrolytic half cell
then 31.75 grams of Copper will be deposited. Two faradays of current will
deposit two eq. masses or 2(31.75) etc. According to the Laws of
Electrolysis developed by Michael Faraday:
weight deposited = (Current in amps) (time in seconds) ( Gram Eq Mass) /
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Electrochemistry, Hydrogen production, Physical chemistry, Electrodes, Industrial gases, Electrolysis, Electrolytic cell, Cathode, Anode, Electroplating, Faraday constant, Electrolyte
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