Question
Explain the working of galvanic cell. How does the electrochemical cell differ from electrolytic cell?
Solution
It is physically impossible to measure te potential difference between a piece of metal and te solution in which it is immersed thus we can use galvanic cell to determine it.
A typical cell might consist of two pieces of metal, one zinc and the other copper, each immersed each in a solution containing a dissolved salt of the corresponding metal. The two solutions are separated by a porous barrier that prevents them from rapidly mixing but allows ions to diffuse through.
right electrde: Cu2+ +2e- ----> Cu
Diffrance between galvanic cell and electrotic cell
A typical cell might consist of two pieces of metal, one zinc and the other copper, each immersed each in a solution containing a dissolved salt of the corresponding metal. The two solutions are separated by a porous barrier that prevents them from rapidly mixing but allows ions to diffuse through.
If we connect the zinc and copper by means of a metallic conductor, the excess electrons that remain when Zn2+ ions emerge from the zinc in the left cell would be able to flow through the external circuit and into the right electrode, where they could be delivered to the Cu2+ ions which become "discharged", that is, converted into Cu atoms at the surface of the copper electrode. The net reaction is the oxidation of zinc by copper(II) ions:
Zn(s)+Cu2+→Zn2++Cu(s)
but this time, the oxidation and reduction steps (half reactions) take place in separate locations:
left electrode : Zn----> Zn2+ +2e-right electrde: Cu2+ +2e- ----> Cu
Diffrance between galvanic cell and electrotic cell
| galvanic cell | Electrolytic cell |
|---|---|
| A Galvanic cell converts chemical energy into electrical energy. | An electrolytic cell converts electrical energy into chemical energy. |
| Here, the redox reaction is spontaneous and is responsible for the production of electrical energy. | The redox reaction is not spontaneous and electrical energy has to be supplied to initiate the reaction. |
| The two half-cells are set up in different containers, being connected through the salt bridge or porous partition. | Both the electrodes are placed in a same container in the solution of molten electrolyte. |
| Here the anode is negative and cathode is the positive electrode. The reaction at the anode is oxidation and that at the cathode is reduction. | Here, the anode is positive and cathode is the negative electrode. The reaction at the anode is oxidation and that at the cathode is reduction. |
| The electrons are supplied by the species getting oxidized. They move from anode to the cathode in the external circuit. | The external battery supplies the electrons. They enter through the cathode and come out through the anode. |
