Electrolysis - Definition, Facts, and Applications

In this article, we will discuss electrolysis - its definition and applications. But, before that let’s have a look into the types of conductors of electricity available in nature.

Types of Conductors

The following two types of conductors of electricity are available in nature:

• Electronic (or Metallic) Conductors
• Ionic (or Electrolytic) Conductors

The common examples of electronic or metallic conductors are silver, copper, aluminium, etc. and examples of electrolytic conductors are solutions of CuSO₄, NaCl, KOH, H₂SO₄, etc.

Characteristics of Electronic Conductors:

• All metals are types of electronic conductors.
• The flow of electric current or electricity takes place due to the movement of free electrons.
• There is no physical or chemical change except the increase in temperature.

Characteristics of Electrolytic Conductors:

• The solutions of acids (H₂SO₄, HCl, etc.), inorganic compounds (NaCl, CuSO₄, AgNO₃, etc.), and Hydroxides of metals (KOH, NaOH, etc.) are examples of electrolytes.
• In electrolytic conductors, the flow of electric current or electricity is due to the movement of ions (oppositely charged atoms) present in the solution.
• An electrolytic conductor does not have free electrons.
• Electrolytes conduct electricity only in their molten state.
• The passage of electric current through an electrolyte causes chemical changes in it.

What is Electrolysis?

The process in which an electric current flows through an electrolyte together with the chemical changes in it is known as electrolysis.

Now, let us understand the process of electrolysis thoroughly. For that consider a copper voltameter as shown in figure-1. In this, when a liquid solution of copper sulphate (CuSO₄) is formed by dissolving the copper sulphate (CuSO₄) in water. The copper sulphate (CuSO₄) breakdowns into its components namely the copper ions (Cu⁺⁺) and the sulphate ions (SO₄^--). Where the copper ions are positively charged and sulphate ions are negatively charged. This process of splitting up the copper sulphate into its components is known as ionization.

Now, when a direct voltage is applied across electrodes of the voltameter, the sulphate ions (SO₄^--) being negatively charged move towards the positive electrode (Anode), and the copper ions (Cu⁺⁺) being positively charged drift towards the negative electrode (Cathode).

When the movement of ions takes place through the electrolyte, the following chemical changes happen:

At Anode (Positive Electrode):

A sulphate ion (SO₄^--) reaches the anode and gives its two extra electrons to the anode and becomes a sulphate radical. These released electrons then flow towards the cathode through the external circuit.

The sulphate radicals chemically react with the anode material to form copper sulphate according to the following reaction:

`\Cu+SO_4→CuSO_4`

Hence, the copper from the anode terminal continuously dissolves into the electrolytic solution as long as the direct voltage is applied.

At Cathode (Negative Electrode):

At the same time, a copper ion (Cu⁺⁺) will reach the cathode, and accepts two electrons from it. These two electrons are the same as that given by the sulphate ion at the anode and have reached the cathode through the external circuit. By accepting these two electrons, the copper ion (Cu⁺⁺) will become a copper atom (Cu) and deposit on the cathode according to the following reaction.

`\Cu^(++)+2e→Cu" atom"`

In this way, the copper material from the solution of copper sulphate (CuSO₄) gets deposited on the cathode of the voltameter.

Important Points about Electrolysis

The following three points are very crucial about the process of electrolysis:

• For electrolysis, direct voltage (DC voltage) is used. It is because we need to attract ions of only one kind to each electrode, i.e. the positive ions to the cathode and the negative ions to the anode.
• The chemical changes during electrolysis take place so long as the direct voltage is applied across the electrodes. When the direct voltage is removed from the electrolyte, the chemical changes will stop.
• During the process of electrolysis, either anode material gets deposited over the cathode or gases are released at the two electrodes.

Applications of Electrolysis

The electrolytic process is being extensively used in different industrial processes. Some popular applications of electrolysis are listed below:

• Electro-Extraction: Electrolysis is used in metal extraction from their ores.
• Electro-Refining: Electrolysis is used in metal refining processes.
• Electrolysis is also used in the electro-deposition and electro-deposition of rubber.
• Electrolysis is used in electroplating.
• Electrolysis is also used in chemical manufacturing.
• Some other applications of electrolysis include electro-cleaning, electro-parting, electro-polishing, anodizing, electro-typing, electro-facing, and electro-foaming.