Faraday's Laws of Electrolysis
- 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
Examples of the Application of Faraday's Laws of Electrolysis
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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