CBSE class 12 ncert chemistry download pdf: Free Chemistry chapter-2 'Electrochemistry'fast track revesion notes.

CBSE class 12 ncert chemistry download pdf: Free Chemistry chapter-2 'Electrochemistry'fast track revesion notes.

              Electrochemistry

1.Cells are the devices in which interconversion of electrical energy and chemical energy takes place. It is of two types:

(i) Electrochemical cell

(ii) Electrolytic cell

2. An electrochemical cell is a device in which chemical energy of the redox reaction is converted into electrical energy. e.g. Daniell cell

3. While writing a cell, the anode is written on the left and the cathode on the right. A vertical line separates the metal from the metal ion (electrolyte solution) and a double vertical line indicates a salt-bridge which is written between the two half-cells (two electrolytes).

The Daniell cell is represented as:

Zn(s)|Zn²+(aq)||Cu ²+(aq)|Cu(s) 

The electrode potential under the conditions of unit concentration at 25°C of all the species in the half-cell is called the standard electrode potential and the electrodes of known potential is known as reference electrode, e.g. standard hydrogen electrode (potential of which is arbitraily taken as zero) and calomel electrode.

5. The potential difference between the electrode potentials of the cathode and anode is called the cell potential.

Electromotive force (emf) is the potential given as 

E°cell = E°cathode-E°anode

6. The arrangement of various standard half-cells in order of their decreasing values of standard reduction potentials is called electrochemical series. If the standard electrode potential of an electrode is greater than zero (positive value) then its reduced form is more stable as compared to hydrogen gas. Similarly, in case of standard electrode potential being less than zero (negative value), hydrogen gas is more stable than the reduced form of the species.

7.Nernst equation is the equation which gives the relation between electrode potential and concentration of metal ions at given temperature Nernst equation for the electrode reaction( half cell reaction) is as follows :

 

8. Gibbs's energy of the reaction The end of a cell is related to the Gibbs's free energy