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ELECTROCHEMISTRY

ELECTROCHEMISTRY. Galvanic cells. MOLAR CONDUCTIVITY. Faraday’s laws of electrolysis. First law: the amount a substance liberated at an electrode during electrolysis is directly proportional to the quantity of electricity which passes through the electrolytic solution. W = Z. I.t.

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ELECTROCHEMISTRY

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  1. ELECTROCHEMISTRY

  2. Galvanic cells

  3. MOLAR CONDUCTIVITY

  4. Faraday’s laws of electrolysis • First law: the amount a substance liberated at an electrode during electrolysis is directly proportional to the quantity of electricity which passes through the electrolytic solution. W = Z. I.t Second law: when the same quantity of electricity is passed thorough the solutions of different electrolytes connected in series the masses of the substances liberated at the electrodes are in the ration of their equivalent masses.

  5. DRY CELL ANODE: ZINC CATHODE: GRAPHITE ROD ELECTROLYTE: MOIST PASTE OF NH4Cl and ZnCl2 Anode Zn(s)→Zn2+ Cathode MnO2 + NH4+→ MnO(OH) +NH3

  6. MERCURY CELL ANODE : Zn(Hg) CATHODE : A PASTE OF HgO and CARBON ELECTROLYTE : A PASTE OF KOH and ZnO ANODE :Zn(Hg) +2OH- → ZnO(s) +H2O + 2e- CATHODE : HgO+ H2O +2e- → Hg(l) +2OH-

  7. LEAD STORAGE CELL ANODE: LEAD CATHODE: A Grid of lead packed with PbO2 ELECTROLYTE: 38% H2SO4 • Anode: Pb + SO4-2 → PbSO4 +2e- Cathode PbO2+SO4-2+ 4H+ +2e- → PbSO4 + 2H2O

  8. Nickel-Cadmium storage cell At anode Cd(s) + 2OH-(aq) → Cd(OH)2(s) + 2e-(Oxidation) At cathode NiO2(s) + 2H2O(l) + 2e_ → Ni(OH)2(s) + 2OH- (Reduction) Over all Cd(s) + NiO2(s) + 2H2O(l) → Cd(OH)2(s) + Ni(OH)2 (s)

  9. NICKEL-CADMIUM CELL Cd(s) +2Ni(OH)3→ CdO(s) + 2Ni(OH)2 (s) +H20(l)

  10. FUEL CELLS At anode H2(g) + 2OH-(aq) → 2H2O + 2 e- At Cathode O2(g) + 2H2O(l) + 4e- → 4OH-(aq) _________________________________ 2H2(g) + O2(g) → 2H2O(l)

  11. CORROSION

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