Work, Energy, and Power
The Chemical Bond
Chemical Thermodynamics and the Equilibrium State
|If the cell voltage is sufficient, negative ions in solution are forced to give up electrons at the positive electrode. The negative ions are oxidized. At the negative electrode, on the contrary, there is a surplus of electrons. These electrons reduce the positive ions in the solution. In an electrolytic cell, oxidation occurs at the positive electrode. (The anode where oxidation occurs is called the anode). The positive electrode is 'pulling' the electrons out. Reduction occurs at the negative electrode, where electrons are being 'pushed' in. The pole where oxidation occurs is termed the anode; the pole where reduction occurs is the cathode.|
The general pattern in electrolysis is for the electrical energy of a DC current to be employed in increasing the internal energy of a chemical system. In simple terms in can be said that an electrolytic cell converts electrical energy into chemical energy. This is a false distinction, though, in the sense that chemical energy is another form of electrical energy. The electrolytic cell transfers electrons from a chemical environment where they exist at a lower electrostatic potential energy (an atom that holds them tightly) to an environment of higher potential energy. In terms of oxidation-reduction, the first atom is oxidized and the second is reduced. In an electrolytic cell, the passage of electricity expends free energy to drive an otherwise nonspontaneous oxidation-reduction reaction.