Faraday’s Laws of Electrosis
Electrochemistry is the Study of relationship between chemical energy and electrical energy and how one can be converted into another. Some of the important metals like Chlorine and Florine are produced from methods of electrochemistry. Battery and fuel cell works on the principles of Electrochemistry.
It is a device capable of either generating electricity from chemical reactions or facilitating chemical reactions through induction of electricity.
This process of carrying out nonspontaneous reactions under the influence of electric energy is termed as electrolysis. Michael Faraday conducted an extensive investigation on electrolysis of solutions and melts of electrolytes. He was the first scientist who described the quantitative aspects of Laws of Electrolysis. He proposed two laws to explain the quantitative aspects of electrolysis popularly known as Faraday’s laws of electrolysis namely, first law of electrolysis and second law of electrolysis:
Faraday’s first law of electrolysis: It is one of faraday’s laws of electrolysis. It states that during electrolysis, the amount of any substance deposited or liberated is directly proportional to the quantity of electricity passed through it.
W ∝ Q
W = ZQ
W = Zit ( Q= I*t )
Where, Z = Electrochemical Equivalent.
Z = atomic weight/nF (n = no. of electron, F = 96500 )
Faraday’s second law of electrolysis:
When the same quantity of electricity is passed through the different electrolytes connected in series. The weights of the substance produced at the electrodes are directly proportional to their equivalent weights.
From these laws of electrolysis, we can deduce that the amount of electricity needed for oxidation- reduction depends on the stoichiometry of the electrode reaction. For example:
Na++e− → Na
As we can observe, one mole of the electron is required for the reduction of one mole of sodium ions. We know that charge on one electron is equal to 1.6021 × 10–19C. Therefore, the charge on one mole of electrons is equal to:
NA × 1.6021 × 10–19C = 6.02 × 1023mol–1 × 1.6021 × 10–19C = 96487 C mol–1
This quantity of electricity is defined as one Faraday and is denoted by F. Hence; one Faraday is defined as the charge carried per unit mole of electrons.
The product of an electrolytic reaction depends on the nature of the material being electrolyzed and the type of electrodes used. In the case of an inert electrode such as platinum or gold, electrode does not participate in the chemical reaction and acts only as source or sink for electrons. While, in the case of a reactive electrode, electrode participates in the reaction. Hence, different products are obtained for electrolysis in the case of reactive and inert electrodes. Oxidizing and reducing species present in the electrolytic cell and their standard electrode potential too, affect the products of electrolysis.