FARADAY'S LAW

physical law stating that the number of moles of substance produced at an electrode during electrolysis is directly proportional to the number of moles of electrons transferred at that electrode; the law is named for Michael Faraday, who formulated it in 1834. The amount of electric charge carried by one mole of electrons (6.02 x 10²³ electrons) is called the faraday and is equal to 96,500 coulombs. The number of faradays required to produce one mole of substance at an electrode depends upon the way in which the substance is oxidized or reduced (see oxidation and reduction). For example, in the electrolysis of molten sodium chloride, NaCl, one faraday, or one mole, of electrons is transferred at the cathode to one mole of sodium ions, Na⁺, to form one mole of sodium atoms, Na, while in the electrolysis of molten magnesium chloride, MgCl₂, two faradays of electrons must be transferred at the cathode to reduce one mole of magnesium ions, Mg⁺², to one mole of magnesium atoms, Mg.

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