electrochemical cells(o2-o4-o9)

ELECTROCHEMICAL CELLS

• conversion of chemical energy to electrical energy

• an apparatus in which a spontaneous reduction oxidation reaction occurs

Parts of a Galvanic Cell

A Galvanic cell is usually separated into two compartments. The reducing and oxidizing species are not in direct contact. Instead an electrical wire is used to facilitate the transfer of electrons and a salt bridge is used to facilitate the transfer of ions.

• cathode - the compartment in which reduction occurs. In the example shown above, the cathode compartment is composed of an aqueous solution of Cu(NO₃)₂ and a copper electrode (an electrode is the material that is exposed to the solution and, at the same time, is connected to an external wire). The reaction at the cathode (a reduction) for this case is:

Cu²⁺ (aq) + 2e^- ---> Cu (s)

• anode - the compartment in which oxidation occurs. In the example shown above, the anode compartment is composed of an aqueous solution of Zn(NO₃)₂ and a zinc electrode. The reaction at the anode (an oxidation) for the above case is:

Zn (s) ---> Zn²⁺ (aq) + 2e^-

In a galvanic cell, electrons are flowing from the anode into the cathode. To complete the electrical circuit, a salt bridge is necessary. Inside the salt bridge, negative ions (anions) move toward the anode (where the positively charged Zn²⁺ is being formed) while positive ions (cations) move toward the cathode (where the amount of positively charged Cu²⁺

half-cell reactions

• oxidation and reduction at electrodes

cell voltage

• electromotive force (E) or cell potential

for more information about electrochemical cells: http://bouman.chem.georgetown.edu/S02/lect25/lect25.htm