In this article, we will explore **Faraday’s laws of electrolysis** – the **First Law of Electrolysis** and the **Second
Law of Electrolysis**. **Michael Faraday**,
an English scientist, performed a series of experiments to know the factors
that control the mass of an element deposited or liberated during the process
of **electrolysis**. Michael Faraday was
the first scientist who explains the quantitative aspects of electrolysis in the
form of his two laws, which are known as Faraday’s laws of electrolysis.

# Faraday’s First Law of Electrolysis

Faraday’s first law of electrolysis is the most fundamental law
of electrolysis.

The statement of Faraday’s first law of electrolysis is as
under:

*During the process of
electrolysis, the mass of an element deposited at an electrode is proportional
to the quantity of electricity which passes through the electrolyte*.

Therefore, if m is the mass of the element deposited at the
electrode, and Q is the quantity of electricity, then according to Faraday’s
first law of electrolysis, we have,

Since *Q
= It*, where *I* is the electric current
and *t* is the time, then

`\m∝It`

`\⇒m=ZIt=ZQ`

Where, *Z* is a constant of proportionality, known as the **electrochemical equivalent (E. C. E.)** of the element deposited at
the electrode during electrolysis. For different elements, *Z* has different values.

## Definition of Electrochemical Equivalent:

In the above equation, if Q = 1 coulomb,
then

Therefore, the **Electrochemical Equivalent (ECE)** of an element is defined as the
mass of the element deposited at the electrode by the passage of 1 coulomb of
electricity through the electrolyte during the process of electrolysis.

The unit of electrochemical equivalent is
g/C or kg/C.

For example, the electrochemical
equivalent of copper is 0.000304 g/C, which means that 0.000304 g mass of
copper will be deposited on the cathode when 1 coulomb of electricity passes
through an electrolytic solution of CuSO_{4}.

# Faraday’s Second Law of Electrolysis

Faradays’ second law of electrolysis
provides a relationship between the mass of an element and the chemical equivalent
weight of that element.

Faraday’s second law is stated as under:

*During
the process of electrolysis, the mass of an element deposited on the electrode is
proportional to the chemical equivalent weight of the element*.

Therefore, if *m* is the mass of the element and *E* is the chemical equivalent weight of the component, then according
to Faraday’s second law of electrolysis, we have,

**Explanation:**

The following figure illustrates Faraday’s second law of electrolysis.

In the shown figure, two voltameter
namely, silver voltameter (with AgNO_{3}) and copper voltameter (with CuSO_{4})
are connected in series. Therefore, they share the same amount of electric
current at the same time. Experimentally, it has been found that the masses of
silver (Ag) and copper (Cu) deposited on the respective cathodes are in the
ratio of 108:32, where 180 is the chemical equivalent weight of silver and 32
is the chemical equivalent weight of copper.

# Relation between Chemical Equivalent and Electrochemical Equivalent

Consider the same quantity of electricity
(Q) is passed through two electrolytes.

If the masses of substances deposited on
the respective electrodes are m_{1} and m_{2}, and their
electrochemical equivalents are Z_{1} and Z_{2} respectively.

Then, according to Faraday’s first law of
electrolysis, we have,

`\m_1=Z_1 Q`

`\m_2=Z_2 Q`

Therefore,

But, according to Faraday’s second law of
electrolysis, we have,

Therefore, from the just above two
equations, we get,

`\Z_1/Z_2 =E_1/E_2`

`\⇒E_1/Z_1 =E_2/Z_2`

In general,

The ratio E/Z is constant for all
substances and it is known as **Faraday
Constant (F)**.

## Definition of Faraday Constant:

Experimentally, the value of the Faraday constant
is found to be 96500 coulombs, thus it can be defined as under:

**Faraday
constant** is defined as the quantity of
electricity required to deposit 1 g of the chemical equivalent of a
substance during the process of electrolysis. Its value is 96500 C.

For example, in a copper voltameter, 96500 C of electricity is to be passed through the electrolyte to deposit the
mass of copper on the cathode equal to 31.75 g, which is the chemical
equivalent of copper.

Hence, this is all about Faraday’s
laws of electrolysis – the first and second laws of electrolysis.

## 0 Comments