1. Since the relevant potential is the difference between half-cell potentials, the zero point is arbitrary. The half-cell zero potential is defined to be for zero for the hydrogen electrode

at 1 atm, 25 and 1 M concentration.
2. All half-cell reactions are written as reductions.
3. Magnitude of the half-cell potential is a measure of the tendency to proceed from left to right (reactions that proceed more readily than the standard hydrogen reaction are assigned a positive voltage).
4. If the direction of the half cell reaction is reversed, the sign of the voltage is reversed. If the half-cell is multiplied to equate electron gain and loss, the voltage remains unchanged.
5. A summation of the half-cell processes must yield a positive value in order for the reaction to occur.
6. For varying concentrations, the Nernst equation must be used,

where is the standard cell potential and n is the number of electrons needed to balance half-cells.
7. To find the half cell potential for a reaction with no tabulated potential, for example

Find two half-reactions which can be combined to yield the desired reaction.


Find the free energy change for each reaction, sum, and calculate the overall for the reaction




Which, in this case,