In this topic, you study the definition, process, uses & diagram of electrolysis.
Whenever an electric current is passed through the electrolyte i.e. the liquid conductor, it decomposes into its ions. This phenomenon is used in electrolysis and electroplating etc. so the electrolysis is defined as, “it is the process in which the electrolyte is decomposed into its ions.” Figure 9.1 shows the example Of electrolysis Of NCI. Two electrodes are immersed in the solution, or the electrolyte of NaCl, The electrodes which is connected to the positive of (the battery is called the anode and that which is connected with the negative is called cathode.
Fig. 9.1. Electrolysis.
Whenever the switch is on, the electric current starts flowing. Now NaCl will decompose into its constituents Na+ and Cl–. Here Na+ being
positively charged will be attracted towards negative cathode and Cl– ions being negatively charged will be attracted towards anode. so
NaCl → Na+ + Cl–
The liberation of these ions and decomposition is known as the electrolysis. It is used in chemical industries for electroplating, electrotyping etc.
Define the following: electrolyte, cathode, anode, ion, anion, cation, chemical equivalent, electro-chemical equivalent, atomic weight and valency.
Electrolyte. It is a liquid conductor or a solution which undergoes the chemical changes when an electric current is passed through it, for example dil. H2S04, solution of CuS04 and AgNq etc. Cathode. It is a metallic plate or electrode which is immersed in electrolyte and is connected to the negative terminal of the battery or the source of supply.
Anode. It is a metallic plate or electrode which is immersed in the electrolyte and is connected to the positive terminal of the battery or source of supply.
Ions. It is a group of the atoms of the same size or molecules of the decomposed electrolyte. These are the charged particles of a solution.
Cation. The charged particles which are having positive charge, are known as cation.
Anion. The charged particles which are having negative charge are known as anion.
Chemical equivalent. The chemical equivalent of a substance is the ratio of atomic weight to the valency.
So chemical equivalent = Atomic weight / Valency
Electro-chemical equivalent. The electro chemical equivalent of the substance is the amount of deposits on passing a steady current of one ampere for one second through the solution.
Valency. The valency of an atom or group of atom is the number of hydrogen atoms with which it will react chemically.
Faraday’s laws of electrolysis.
Faradays established two well known laws regarding the electrolysis, which are named as the Faraday’s laws Of electrolysis.
1st law. The weight of the liberated or deposited ions during electrolysis is directly proportional to the quantity of electricity which is passed through
so
where
m = Mass of the liberated ions
q =Quantity of electricity i.e. It
I =Current in amperes
t = Time in seconds
m ∝ It
Z is the electro-chemical equivalent of the substance. If one ampere current is passed for one second then
i.e., the electro-chemical equivalent is defined as the mass of the liberated ions when one ampere current is passed through the electrolyte for one second.
Second law. Whenever the same quantity of electricity is passed through different electrolytes the amount of the different substances liberated is directly proportional to their chemical equivalents
and
k, etc.
What are the main applications of electrolysis?
The phenomenon of electrolysis is of great importance and has so many applications. Some of these applications are as under:
(a) Electroplating,
(b) Extraction and purification Of metals,
(c) Electrotyping.
