Electrochemistry: Types of Electrochemical Cell, the Daniell Cell (For CBSE, ICSE, IAS, NET, NRA 2022)

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  • A device that generates a potential difference between electrodes by chemical reactions is called an electrochemical cell.
  • Electrochemistry is the branch of physical chemistry that studies the relationship between electricity, as a measurable and quantitative phenomenon, and identifiable chemical change, with either electricity considered an outcome of a particular chemical change or vice versa.
  • It comprises two electron conductors which are separated by an ionic conductor and are linked by an electron conductor.
  • The two metallic electrodes are dipped in the electrolytic solution. The important component of this cell is an ionic conductor.
  • Electrochemistry is the study of chemical processes that cause electrons to move. This movement of electrons is called electricity, which can be generated by movements of electrons from one element to another in a reaction known as an oxidation-reduction reaction.
  • A redox reaction is a reaction that involves a change in oxidation state of one or more elements.
  • When a substance loses an electron, its oxidation state increases; thus, it is oxidized.
  • When a substance gains an electron, its oxidation state decreases, thus being reduced. For example, for the redox reaction

Types of Electrochemical Cell

Types of Electrochemical Cell
  • Electrochemical cells are of two types.
  • Galvanic cell and Electrolytic cell.
  • Galvanic cell – In a galvanic cell, spontaneous redox reaction, the chemical energy is converted into electrical energy. It is also called voltaic cell or Daniel cell.
  • Electrolytic cell – In an electrolytic cell, the no spontaneous redox reaction is carried out by electrical energy.
  • We can obtain the standard potential of the cell by taking the difference between the standard potentials of anode and cathode.

Properties of Galvanic and Electrochemical Cells

The Electrochemical Cell

The Daniell Cell

The Daniell Cell
  • In electrochemical cells, reactions take place at separate electrodes - and indeed the electrodes themselves may be placed in different vessels. Consider one of the early galvanic cells, the Daniell cell.
  • The Daniell cell՚s source of energy is the spontaneous reaction of zinc metal with copper sulfate to produce zinc sulfate and copper metal.

Zn (s) + Cu2 + (aq) ⇾ Zn2 + (aq) + Cu (s) ΔG° =-212.6 kJ mol-1

When the materials are brought together:

  • in direct contact in one vessel, chemical potential energy is converted into thermal energy and the reaction vessel gets warmer
  • in an electrochemical cell, chemical potential energy is converted into electrical energy