Faraday's Laws of Electrolysis

Key Concepts

First Law :
The mass of a substance produced by electrolysis is proportional to the quantity of electricty used.
In order to produce more substance electrolytically we must use more electricity.
Second Law:
^* The amount of electricity in coulombs required to produce 1 mole of a substance is a simple whole number multiple of 96 500^#
The quantity 96,500 is given the name the Faraday (or Faraday Constant) and the symbol F
F is equal to the quantity of electricity carried by one mole of electrons:
F = Avogadro's Number x charge on electron in coulombs = 6.022 x 10²³ mol^-1 x 1.602192 x 10^-19 C
F = 96,484 C mol^-1 (usually rounded up to 96,500 C mol^-1 in high school chemistry)
Faraday's Laws of Electrolysis Calculations: Q = n(e^-) x F
Q = quantity of electricity measured in coulombs (C)
n(e^-) = moles of electrons used
F = the Faraday (Faraday constant) = 96,500 C mol^-1
We can calculate the mass of a substance produced during an electrolysis experiment by:
i) calculating the moles of electrons used: n(e^-) = Q/F
ii) calculating the moles of substance produced using the balanced reduction (or oxidation) half reaction equation
iii) using the moles of substance to calculate the mass of substance: mass = moles x molar mass

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^* More formally we say that for a given quantity of electricity the quantity of substance produced is proportional to its equivalent weight.

^#The figure is closer to 96,484 but is usually rounded off to 96,500 for school chemistry calculations

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