. Discuss the process of Half cell and Electrodes


Best Answer

A piece of zinc, called the zinc electrode (a solid metal rod connected to the external circuit), is immersed in a solution of zinc (II) sulphate, and a piece of copper, the copper electrode, is immersed in a solution of copper (II) sulphate. The two solutions are kept apart by a porous barrier that permits ions to move from one solution to the other but prevents the two solutions from mixing. A conducting metal wire connects the two electrodes. At the surface of the zinc electrode, Zinc atoms are oxidized to Zn2+ ions, which pass into solution. The electrons lost by the zinc atoms leave the electrode and flow through the wire to the copper electrode. Here they reduce Cu2+ ions, so a deposit of copper forms on the surface of the electrode. The electrode at which reduction occurs is called cathode and the electrode at which oxidation occurs is called anode.The two compartments of the cell are called half cells. The zinc electrode dipping into a zinc sulphate solution is one half-cell, and the copper electrode dipping into a copper sulphate solution the other half - cell.

Any electrochemical cell consists of two half-cells, oxidation takes place in one, and reduction takes place in the other. Neither half cell reaction can take place by itself, because each must be accompanied by another half cell reaction that uses up or supplies the necessary electrons. These electrons constitute the electric current that flows through the external circuit. Not only must the circuit be complete outside the cell, but it must be complete inside as well; that is, ions must be able to move from one electrode to the other. This movement is made possible by separating the half cells with a porous partition (of clay pottery, for example)or a salt bridge.

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