When electricity causes a chemical reaction, then this process is called electrochemistry. There is a definite relationship between electrical energy and chemical energy.
The branch of chemistry in which the relationship between electrical energy and chemical energy and their transformation into each other is studied is called electrochemistry.
Under electrochemistry, those chemical reactions are studied in which electrical energy is liberated or absorbed, these reactions can be of two types –
Electro – Chemical Cell
When an electric current is passed through the molten state of certain substances or their solutions, the substance decomposes into its constituent parts.
Example: By passing an electric current through water in the presence of dilute acid, water decomposes into its constituents oxygen (O2) and hydrogne (H2).
2H2O → 2H2 + O2
Such substances which get decomposed into their components by passing current are called Electrolytes and this process is called electrolysis. Usually acids, bases and salts are electrolytes.
Electrolytes are made up of electrically charged particles called ions. There are two types of Ions, which have positive electric charge, they are called cations and those which have negative electric charge are called anions.
Similarly, electric current cannot flow in solid sodium chloride, so solid sodium chloride is first brought to the molten state. For this, a heater is used inside the decomposition cell. When sodium chloride is molten, when electric current is passed through it, due to the legal decomposition of sodium chloride, sodium is obtained at the cathode and chlorine gas is obtained at the anode.
2NaCl + Energy (Electric Current) → 2Na + Cl2
Therefore, electrolytes are the reactions in which a molten or aqueous solution of a compound is chemically decomposed by the effect of electric current.
A special device is used for electrolytes, which is called an electrolytic cell.
In an electrolytic cell, molten sodium chloride breaks down into sodium ion (Na+) and chloride ion (Cl–).
NaCl → Na+ + Cl–
The positively charged ions (Na+) are attracted to the negatively charged electrode cathode and get converted into sodium atom after gaining one electron.
at the cathode
Na+ + e– → Na (reduction)
The acquisition of electrons is called reduction. Here Na+ is reduced to Na. The negative ions (Cl–) are attracted to the positively charged electrode anode and change into a chlorine atom by removing an electron. Two chlorine atoms combine to form a chlorine molecule (gas).