3. CELL CELL IS A DEVICE WHICH CONVERT CHEMICAL ENERGY INTO ELECTRICAL ENERGY AND VICE VERSA

5.  Electric current forces charges on electrodes + + + – – – Na + Cl – Na + takes up an electron: Na + (aq) + e –  Na Cl – gives up an electron: 2Cl – (aq)  Cl 2 + 2e – Thus electricity continues to flow Pure Na is deposited, Cl 2 gas is produced Na + is attracted to negative, Cl – to positive

6. At anode zn-------------------  zn 2+ +2e- At cathode 2 MnO2+2NH4++2e---  Mn2O3 +H2O+2NH3( ) NH3 IS CONSUMED IN COMPLEX FORMATION WITH Zn 2+ ION Zn2 + +4NH 3 ----------------  [Zn(NH3)4} 2+ ----- ------  [Zn(NH3)4]Cl 2 At anode Zn-------------------  Zn 2+ + 2e- At cathode 2 MnO 2 +2NH 4 ++2e---  Mn 2 O 3 +H 2 O+2NH 3 ( ) NH 3 IS CONSUMED IN COMPLEX FORMATION WITH Zn 2+ ION Zn 2+ +4NH 3 ---  [Zn(NH 3 ) 4 } 2+ -------- 2Cl- -----  [Zn(NH3)4]Cl 2

8. ELECTRODE REACTIONS IN LEAD STORAGE BATTERY

9. Cathode: O2(g) + 2H2O(l ) + 4e–→ 4OH–(aq) Anode: 2H2 (g) + 4OH–(aq) → 4H2O(l) + 4e– OVERALL REACTION 2H2(g) + O2(g) → 2 H2O(l )

10. MERITS OF FUEL CELL ECO FRIENDLY CONTINUOUS SOURSE OF ENERGY HIGH EFFICIENCY DEMERITS OF FUEL CELL VERY EXPENSIVE HEAVY NOT CONVENIENT TO USE HIGHLY CORROSIVE NATURE OF THE ELECTROLYTE