This means that their operation is totally opposite in direction, in fact a rechargeable battery can act as both a voltaic cell and an electrolytic cell depending on whether it is discharging or being charged. It is also practical to use the same type of metal as electrodes in an electrolytic cell while in voltaic cells the electrodes must be of different metals. Since sodium is too reactive to freely occur naturally it exists in the earth's crust in a number of varied compounds such as halite. It can also be found in the form of sodium chloride and brine which are plentiful sea water. These compounds can be obtained by trapping the sea water or brine, or by mining rock salt. In order to obtain pure sodium metal, electrolysis of molten sodium chloride is done. This is achieved by using the molten sodium chloride as the electrolyte in an electrolytic cell. Molten sodium chloride contains free sodium ions and chloride ions, these can separate from one another thus move about in the liquid. The chloride ions...

The breaking apart of the molten sodium chloride can be represented using the following equation.
NaCl (l) ? 2Na (l) + Cl2 (g)

The half-reactions taking place in this process are:

Reduction: 2Na+(l) + 2e- ? Na(s) E" = -2.71 V

Oxidation 2Cl-(l) ? Cl2 (g) + 2 e- E" =-1.36V