Shaillee Kaushal is teaching live on Unacademy Plus
XII- 03 Electrochemistry -VI
Electrode potential When a metal is placed in a solution of its ions, the metal acquires either a positive or a negative charge with respect to the solution Due to this a definite potential difference is developed between the metal and the solution. This potential difference is called electrode potential
Reference elctrode: it is not possible to measure the absolute value ofa single electrode potential directly. On the difference in potential between two electrodes can be measured experimentally > For this purpose reference electrode is used. The e.m.f of the resultant cell is measured experimentally Ecell EAnode + Ecathode - Oxidation potential +Reduction potential. > Knowing the value of reference electrode, the value of other electrode can be determined.
at 1 atm) > The hydrogen elctrode can act as a cathode or anode with respect to other elctrode. H30+ (aq.) If cathode: If anode 2H+ + 2e- H2
Determination of standard electrode potential of Zn/Zn2+ electrode A zinc rod is dipped in 1M ZnSO, solution. This half cell is combined with a standard hydrogen electrode through a salt bridge. The cell can be representedby: Voltmeter ! cathode Zn rod (Anode) Zn(s)Izn2+ (aq)112n+(aq)|H2(g) Salt bridge H2 (at 1 atm) Oxidation Reduction The e.m.fof the cell is recorded 0.76 V cell : Anode + cathode 0.76Eode 0 So Eanode0.76 1M ZnSO4 1M HCI As oxidation takes place at the anode the reduction potential of Zn i.e n2+1Zn-0.76V
(ii) Determination of standard elctrode poten tial Cu2+ /Cu electrode Valve voltmeter The cell can be representedas Electron flow if metal M has a nogative electrode 21 (aq) potential Electron flow if metal M has a positive electrode potential The e.m.fof the cell is recorded 0.34V Salt bridge E cell Eo anode + E cathode 0.34 0 + E cathode Ecu?+/Cu-0.34% Hydrogen Metal M Molar M Molar Ht