Electrochemistry is built around devices that can interconvert electrical energy and chemical energy. These devices are called electrochemical cells. There are two fundamental types of electrochemical cells: galvanic (voltaic) cells and electrolytic cells. They are distinguished by the direction in which the energy conversion occurs.
Definition
Electrochemical cells are devices that convert electrical energy into chemical energy and vice versa. There are two types:
Galvanic (Voltaic) Cells: These convert chemical energy from a spontaneous redox reaction into electrical energy.
Electrolytic Cells: These use electrical energy from an external source to drive a non-spontaneous chemical reaction.
Core Concept
The core concept is the relationship between the spontaneity of the redox reaction and the direction of energy conversion.
In a galvanic cell, the redox reaction is spontaneous (has a positive cell potential, E°cell > 0). The chemical energy of the reaction is released and harnessed as electrical work.
In an electrolytic cell, the redox reaction is non-spontaneous (has a negative cell potential, E°cell < 0). An external power source must supply electrical energy to force the reaction to occur in the reverse, non-spontaneous direction.
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