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+ + 8H2O
Therefore, quantity of electricity required to reduce 1 mole of Cr2 O72- = 6 F
= 6 × 96487 C
= 578922 C