electrolytic cells

Electrolytic Cells

• conversion of electrical energy back to chemical energy
• decomposes chemical compounds by means of electrical energy, in a process called electrolysis; the Greek word lysis means to break up. The result is that the chemical energy is increased. Important examples of electrolysis are the decomposition of water into hydrogen and hydroxide, and bauxite into aluminium and other chemicals.(http://en.wikipedia.org/wiki/Electrolytic_cell)

E^o_cell = E^o_reduction(cathode reaction) - E^o_reduction(anode reaction)

If E^o_cell> 0, we have a spontaneous process (galvanic cell)
If E^o_cell<>

THREE COMPONENTS OF ELECTROLYTIC CELLS:

• electrolyte (any substance containing free ions that behaves as an electrically conductive medium)
• 2 electrodes: anode and cathode

Galvanic cells compared to electrolytic cells

In contrast, a battery or galvanic cell, converts chemical energy into electrical energy, by using spontaneous chemical reactions that take place at the electrodes. Each galvanic cell has its own characteristic voltage (defined as the energy release per electron transfer from one electrode to the other). A simple galvanic cell will consist only of an electrolyte and two different electrodes. (Galvanic cells can also be made by connecting two half-cells, each with its own electrode and electrolyte, by an ion-transporting "bridge", usually a salt bridge; these cells are more complex.) The electrodes typically are two metals, which naturally have different reaction potentials relative to the electrolyte. This causes ions of one of the electrodes to preferentially enter the solution at one electrode, and another ion to leave the solution at the other electrode. This generates an electric current across the electrolyte, which will drive electric current through a wire that makes an exterior connection to each of the electrodes. A galvanic cell uses electrodes of different metals, whereas an electrolytic cell may use the same metal for cathode and anode.

A rechargeable battery, such as a AA NiMH cell or a single cell of a lead-acid battery, acts as a galvanic cell when discharging (converting chemical energy to electrical energy), and an electrolytic cell when being charged (converting electrical energy to chemical energy).(http://en.wikipedia.org/wiki/Electrolytic_cell)

for more information: http://en.wikipedia.org/wiki/Electrolytic_cell