Electrochemistry: Products of Electrolysis, Galvanic Cell and Salt Bridge (For CBSE, ICSE, IAS, NET, NRA 2022)

Get unlimited access to the best preparation resource for competitive exams : get questions, notes, tests, video lectures and more- for all subjects of your exam.

Products of Electrolysis

  • During electrolysis, cations are reduced at cathode and anions are oxidized at anode and a chemical reaction occurs in a non-spontaneous direction.
  • The minimum potential required for any electrode process to occur is called its discharge potential or decomposition potential.
  • There are some examples of electrolysis.

Electrolysis of Molten (Pt Electrodes)

Molten furnishes its own cations and anions.

Anodic process (oxidation) :

Cathodic process (reduction) :

Electrolysis of Aqueous ( Electrodes)

Dissolved ionizes in its solution as

At Cathode

  • At cathode ions and also can be reduced.
  • The reduction potential of water is much greater than that of .

Therefore, only gas is evolved at cathode

At Anode

  • At anode, ions and both can get oxidized.
  • Oxidation potential of water is slightly greater than that of so its oxidation should be easier. Therefore, gas is evolved at anode.

Galvanic Cell

Galvanic cell used to produce electricity.

When a Zinc rod is dipped in solution, a reaction starts in the solution.

It is an example of redox reaction. The two half reactions are

Oxidation

Reduction

  • In this redox reaction the electrons given by zinc rod have been directly consumed by ion.
  • The electrons given by Zinc rod to flow through a wire to reach ions and producing electric current.
  • The reaction carried out in the electrochemical cell as shown Fig.
Galvanic Cell
  • In Electro chemical cell , Zinc rod is dipped in zinc sulphate solution in one beaker while copper rod is dipped in another beaker containing solution.
  • The two solution are connected through a salt bridge and the two metals are connected to an ammeter with the help of wire and find electrons move through the wire from zinc to copper rod.
  • A metal dipped in its own salt solution is called as half-cell.
  • Zinc rod dipped in-zinc sulphate solution is oxidation half-cell because oxidation takes place.

(oxidation)

  • Zinc rod release electron and becomes negatively charged
  • Copper in copper sulphate is reduction half-cell.

  • Copper red gain electrons and becomes positively charged
  • The electrons released at the anode during oxidation flow through the external circuit and reach the cathode where they are taken up for reduction and form a conventional positive current flows in the opposite direction.

Salt Bridge

  • A salt bridge is an inverted tube filled with a concentrated solution of an inert electrolyte like or which does not take part in the cell reaction.
  • It completes the inner circuit. It acts as a contact between the two half cells without any mixing of electrolytes.
  • It prevents accumulation of charges in two half cells and maintains electrical neutrality.

Symbolic Representation of Galvanic Cell

The rules of representation are as follows:

  • Anode is written on the left-hand side and cathode on the right-hand side.
  • The metal electrode in the anode half-cell is written by its symbol and this is followed by the cation (metal ion) along with its concentration in a small bracket. The metal and cations are separated by vertical line.

In the reduction half-cell the anion along with its concentration is written first, then vertical line and then the metal.

A salt bridge is represented by two vertical lines.

Thus, the Galvanic cell is written as

Developed by: