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Electrochemistry

Galvanic Cells

Electrochemical Cell

  • An electrochemical cell is a cell used for generating electrical energy from chemical reactions, or for inducing chemical reactions from electrical energy.

  • Daniel cell

  • Generates electrical energy from the chemical reaction

  • Electrode potential = 1.1 V, when = 1 mole dm−3

  • Such a device is called a galvanic or voltaic cell.

  • When an external potential is applied and increased slowly, the reaction continues till Eext = 1.1 V. At this external potential, the reaction stops; when Eext is further increased, the reaction starts again, but in the opposite direction. Now, the device becomes an electrolytic device.

  • When Eext < 1.1 V

(i) Electrons flow from the Zn rod to the Cu rod, so current flows from Cu to Zn

(ii) Zn dissolves at the anode and copper deposits at the cathode

  • When Eext = 1.1 V

(i) There is no flow of electrons, and hence, there is no current

(ii) No chemical reaction takes place

  • When Eext > 1.1 V

(i) Electrons flow from the Cu rod to the Zn rod, so current flows from Zn to Cu

(ii) Copper dissolves at the Cu electrode and Zn deposits at the Zn electrode.

Galvanic Cells

  • Convert chemical energy of a spontaneous redox reaction into electrical energy

  • Example: Daniel cell

  • The overall cell reaction is

  • Reduction half-reaction:

  • Oxidation half-reacti...

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