Electrolysis

In chemistry, the production of chemical changes by passing an

electric current through a solution or molten salt (the electrolyte),

resulting in the migration of ions to the electrodes: positive ions

(cations) to the negative electrode (cathode) and negative ions

(anions) to the positive electrode (anode).

During electrolysis, the ions react with the electrode, either

receiving or giving up electrons. The resultant atoms may be liberated

as a gas, or deposited as a solid on the electrode, in amounts that

are proportional to the amount of current passed, as discovered by

English chemist Michael Faraday. For instance, when acidified water is

electrolysed, hydrogen ions (H+) at the cathode receive electrons to

form hydrogen gas; hydroxide ions (OH-) at the anode give up electrons

to form oxygen gas and water.

One application of electrolysis is electroplating, in which a solution

of a salt, such as silver nitrate (AgNO3), is used and the object to

be plated acts as the negative electrode, thus attracting silver ions

(Ag+). Electrolysis is used in many industrial processes, such as

coating metals for vehicles and ships, and refining bauxite into

aluminium; it also forms the basis of a number of electrochemical

analytical techniques, such as polarography.

Faraday's laws

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Three laws of electromagnetic induction, and two laws of electrolysis,

all proposed originally by English scientist Michael Faraday:

Induction (1) a changing magnetic field induces an electromagnetic

force

In a conductor; (2) the electromagnetic force is proportional to the

rate of change of the field; (3) the direction of the induced

electromagnetic force depends on the orientation of the field.

Electrolysis (1) the amount of chemical change during electrolysis is

proportional to the charge passing through the liquid; (2) the amount

of chemical change produced in a substance by a given amount of

electricity is proportional to the electrochemical equivalent of that

substance.

Faraday's constant

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Constant (symbol F) representing the electric charge carried on one

mole of electrons.