. Electrochemical Cell Electrochemical cell is a device which converts chemical energy into electrical energy and vice versa. It consists of two separate electrodes which are in contact with an electrolyte solution. Electrochemical cells are mainly classified into the following two types.
. Galvanic Cell ( Voltaic cell) : It is a device in which a spontaneous chemical reaction generates an electric current i.e., it converts chemical energy into electrical energy. It is commonly known as a battery. .
Electrolytic cell : It is a device in which an electric current from an external source drives a nonspontaneous reaction i.e., it converts electrical energy into chemical energy. XII U9 Electro XII U9 Electro - - - - . . Galvanic cell We have already learnt in XI standard that when a zinc metal strip is placed in a copper sulphate solution, the blue colour of the solution fades and the copper is deposited on the zinc strip as red – brown crust due to the following spontaneous chemical reaction.
Zn(s) + CuSO (aq) ZnSO (aq) + Cu (s) The energy produced in the above reaction is lost to the surroundings as heat. In the above redox reaction, Zinc is oxidised to Zn + ions and the Cu + ions are reduced to metallic copper. The half reactions are represented as below. Zn(s) Zn (aq) + 2e (oxidation) + Cu (aq) + 2e Cu (s) (reduction) + - → If we perform the above two half reactions separately in an apparatus as shown in figure .
, some of the energy produced in the reaction will be converted into electrical energy. Let us understand the function of a galvanic cell by considering Daniel cell as an example. It uses the above reaction for generation of electrical energy. The separation of half reaction is the basis for the construction of Daniel cell.
It consists of two half cells. Oxidation half cell A metallic zinc strip that dips into an aqueous solution of zinc sulphate taken in a beaker, as shown in Figure . . Reduction half cell A copper strip