Ask a Teacher

How will a electrochemical cell works? How does the circuit is completed?

The chemical reaction which takes place in a cell like Daniell cell is called an electrochemical reaction .An electrochemical reaction can be carried out in a specially designed set up called an electrochemical cell .

Electrochemical cells are of two types :

1.Electrolytic cells

2.Galvanic (voltaic cells )

 In electrolytic cells ,electrical energy is used to bring about a chemical reaction or a chemical change .

In galvanic cells,chemical energy of the reacting substances is converted into electrical energy .For example ,in Daniell cell ,the free energy of the reaction 

Cu²⁺(aq)        +       Zn(s)     ____________>     Zn²⁺(aq)      +    Cu(s)

is converted into electrical energy .Under standard conditions, the cell produces an EMF of 1.1 V 

Illustration of galvanic cell : In Daniell cell ,current flows from copper electrode to zinc electrode. Under standard conditions ,this cell produces an emf of 1.1 V

The reaction takes place in Daniell cell are 

Zinc electrode          :     Zn(s)             __________>     Zn²⁺(aq)  +  2e^-

Copper electrode  :          Cu²⁺(aq) +   2e^-   ___________>     Cu (s)

_____________________________________________________

Net reaction   :      Zn(s)     +     Cu²⁺(aq)   __________>    Zn²⁺(aq)     +Cu (s)   

 The schematic diagram of  Daniell cell