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Electrolytic Cells


Key Terms:


Unlike the voltaic wet and dry cells, electrolytic cells consume electricity in order to produce a chemical product that will not spontaneously occur.  The process of using energy to make the nonspontaneous product is called electrolysis.

uses energy
contains an external electrical source
terminals often inert do not participate in redox reactions (just transfer e-)
electrons flow from the anode to the cathode

Electrolysis of water

Water is the foundation of life on our planet.  It is very stable and, although undergoing self-ionization, does not spontaneously separate into its H2 and O2 parts.  Electrolysis of water takes place in the presence of electricity.

2H2O(l) g 4 H+ (aq) + O2(g)+ 4e-
4H2O(l) + 4e- - (aq) g 2H2(g)

Although the hydrogen that is produced in the reaction may be used to power a commercial fuel cell, the reaction uses more energy than is produced by the fuel.  A better way to obtain the fuel is through electrolysis of aqueous sodium chloride.


Electrolysis of Aqueous Sodium Chloride. (brine solution)

The formation of hydrogen, chlorine, and sodium hydroxide are the products of the electrolysis reaction.  Since all of the products are commercially desirable, the cost of hydrogen production is less than the energy benefit for the fuel cells it powers.

2Cl-(l) g Cl2(g)+ 2e-
2H2O(l) + 2e- g 2 OH- (aq) + H2(g)
NA is considered a spectator ion
it is present in both of the half reactions



Electroplating is used to deposit a thin coat of metal on another metallic object.  

the plating is often used to protect a surface from corrosion and oxidation
plating is done to reduce the cost of jewlery


Last modified: May 21, 2004