Electrolysis

The process of decomposition of solution into ions on passing the current through it is called electrolysis.

Electrolyte

It is a substance which allows the current to pass through it and also decomposes, into positive and negative ions. For example, acids, bases, salts dissolved in water, alcohol are common electrolytes. AgI is a solid state electrolyte and KCl, NaCl are electrolyte in their molten state.

Voltameter

The vessel containing electrodes and electrolyte, in which the electrolysis is carried out is called a voltameter.

Cations

The ions which carry positive charge and move towards the cathode during electrolysis are called cations.

Anions

The ions which carry negative charge and move towards the anode during electrolysis are called anions.

Faraday’s laws of electrolysis

1) First law- The mass of the substance liberated or deposited at an electrode during electrolysis is directly proportional to the quantity of charge passed through the electrolyte.

2) Second law- When same amount of charge is passed through different electrolytes, the masses of the substance liberated or deposited at the various electrodes are proportional to their chemical equivalents. i.e. m1/m2=E1/E2 . Where m1, m2 are the masses of the substances liberated or deposited on electrodes during electrolysis and E1 and E2 are their chemical equivalents.

Faraday constant

1) F= E/z=Eq/m if m=E, then F=q.
2) Thus Faraday constant is equal to the amount of charge required to liberate the mass of a substance at an electrode during electrolysis, equal to its chemical equivalent in grams (i.e. one gram equivalent)

3) One Faraday = 1F= 96500 C/gram equivalent.
4) Faraday constant, F= Ne; where N is Avogardo’s number and e is the charge of an electron.

5) If M is the atomic mass of one mole of a substance and p is the valence of this substance, then Faraday constant, F = E/z=M/pz
6) 96500 C charges are required to liberate or deposit 1.008g of hydrogen or 31.5g Cu or 108g of silver on cathode during electrolysis.

Electroplating

1) It is a process depositing a thin layer of one metal over another metal by the method of electrolysis.

2) By the process of electroplating, the articles of cheap metals are coated with the precious metals like silver and gold to make their look more attractive.

3) The article to be electroplated is made the cathode. And the article to be deposited is made the anode. A soluble salt of precious metal is taken as electrolyte.