Class 12 Chemistry Electrochemistry Faradays Laws of Electrolysis

Faraday’s Laws of Electrolysis

  • Michael Faraday described the quantitative aspects of electrolysis and came forward with two laws of electrolysis:
  • 1st Law: The amount of chemical reaction which occurs at any electrode during electrolysis by a current is proportional to the quantity of electricity passed through the electrolyte (solution or melt).
  • 2nd Law: The amounts of different substances liberated by the same quantity of electricity passing through the electrolytic solution are proportional to their chemical equivalent weights
  • Mathematically, Atomic Mass of Metal ÷ Number of electrons required to reduce the cation.

Q = It
where Q
is in coloumb

I is in ampere and

t is in second.

  • This quantity of electricity is known as Faraday and is represented by the symbol F.

  • In the above example application of more current results in the deposition of more amount of copper from the anode to the cathode.



If a current of 0.5 ampere flows through a metallic wire for 2 hours, then how many electrons would flow through the wire?


I = 0.5 A

t = 2 hours = 7200 s

By using the formula, Q = It

= 0.5 A × 7200 s

= 3600 C

We know that 96487C = 6.023 X 1023 number of electrons.

Now, 3600 C =  number of electrons. Hence, 2.25 X 1022number of electrons will flow through the wire.



Consider the reaction:  Cr2 O72- + 14H+ + 6e- → Cr3+ + 8H2O. What is the quantity of electricity in coulombs needed to reduce 1 mol of Cr2 O72-?


Cr2 O72- + 14H+ + 6e- → Cr3+ + 8H2

Therefore, quantity of electricity required to reduce 1 mole of Cr2 O72- = 6 F

= 6 × 96487 C

= 578922 C


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