Class 12 Chemistry Electrochemistry Faradays 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?

Solution:

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.

Problem:

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-?

Solution:

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

.