Class 12- Electrochemistry || trick to solve numericals on faraday's law of electrolysis|| NEET/ IIT

Faraday’s Laws of Electrolysis

Before understanding Faraday’s laws of electrolysis, we must first understand the process of electrolysis of a metal sulfate.

Whenever an electrolyte like metal sulfate is diluted in water, its molecules split into positive and negative ions. The positive ions (or metal ions) move to the electrodes connected with the negative terminal of the battery where these positive ions take electrons from it, becoming a pure metal atom and getting deposited on the electrode.

The negative ions (or sulphions) move to the electrode connected with the positive terminal of the battery, where these negative ions give up their extra electrons and become SO4 radical. Since SO4 cannot exist in an electrically neutral state, it will attack the metallic positive electrode – forming a metallic sulfate which will again dissolve in the water.

Faraday’s laws of electrolysis are quantitative (mathematical) relationships that describe the above two phenomena. 



Faraday’s First Law of Electrolysis states that the chemical deposition due to the flow of current through an electrolyte is directly proportional to the quantity of electricity (coulombs) passed through it.

Faraday’s Second Law of Electrolysis

So far we have learned that the mass of the chemical, deposited due to electrolysis is proportional to the quantity of electricity that passes through the electrolyte. The mass of the chemical, deposited due to electrolysis is not only proportional to the quantity of electricity passes through the electrolyte, but it also depends upon some other factor. Every substance will have its own atomic weight. So for the same number of atoms, different substances will have different masses.

Again, how many atoms deposited on the electrodes also depends upon their number of valency. If valency is more, then for the same amount of electricity, the number of deposited atoms will be less whereas if valency is less, then for the same quantity of electricity, more number of atoms to be deposited.