GALVANIC CELL

GALVANIC CELL

• A device used to convert chemical energy produced in a redox reaction into electrical energy is called a galvanic cell or voltaic cell.


• Device set up :- There are two separate beakers, called half-cells or redox couples. Zinc sulphate solution is taken in one beaker and copper sulphate solution is taken in another beaker. A zinc rod is placed in zinc sulphate solution taken beaker. A copper rod is placed in copper sulphate solution taken beaker. These rods are called electrodes. These electrodes are connected by a wire and the two solutions are connected by a salt bridge.


• Oxidation takes place at aonde , here zinc electrode is anode.Zinc produces electrons which move through the connecting wire to the cathode.Zinc ions go to the zinc sulphate solution.
  Zn(s) → Zn²⁺(aq) + 2e^-


• Reduction takes place at cathode , here copper electrode is cathode.Copper ions in the solution gain electrons and deposited at cathode as copper atoms.
  Cu²⁺(aq) + 2e^- → Cu(s)


• Poles :- Anode is negative (-ve) pole while cathode is positive (+ve) pole.


• Direction of current:- Electrons move from anode to cathode and the conventional current flows from cathode to anode through the connecting wire.


• The oxidation of zinc into ions produces the excess of Zn²⁺ ions in the left beaker. Similarly, the reduction of copper ions to copper atoms leaves the excess SO₄^2- ions in the solution in the right beaker. To maintain electrical neutrality of the solutions in the two beakers , the cations and the anions move through the salt bridge. This helps to complete the inner circuit.


• Obviously , the weight of the copper rod will increase while that of zinc rod will decrease as the cell works.


• REPRESENTATION OF GALVANIC CELL:-
  Zn | Zn²⁺(c₁) || Cu²⁺(c₂) | Cu



• ELECTRODE POTENTIAL:-
  The electrical potential difference set up between the metal and its ions in the solution is called electrode potential.
  or
  The tendency of an electrode to lose or gain electrons when it is in contact with solution of its own ions is called electrode potential.
  Two types of electrode potential:-
  (A) Oxidation Potential:- It expresses the tendency of losing electrons. For a metal M , it is represented as E_M|Mⁿ⁺
  (B) Reduction Potential:- It expresses the tendency of gaining electrons. For a metal M , it is represented as E_Mⁿ⁺|M