23.2. Cell Potentials http://www.ck12.org
TABLE23.2:(continued)
Half Reaction Eo(V)
Fe^3 ++ e−→Fe^2 + +0.77
I 2 + 2e−→2I− +0.53
Cu++ e−→Cu +0.52
O 2 + 2H 2 O + 4e−→4OH− +0.40
Cu^2 ++ 2e−→Cu +0.34
Sn^4 ++ 2e−→Sn^2 + +0.13
2H++ 2e−→H 2 0.00
Pb^2 ++ 2e−→Pb −0.13
Sn^2 ++ 2e−→Sn −0.14
Ni^2 ++ 2e−→Ni −0.25
Co^2 ++ 2e−→Co −0.28
PbSO 4 + 2e−→Pb + SO 42 − −0.31
Cd^2 ++ 2e−→Cd −0.40
Fe^2 ++ 2e−→Fe −0.44
Cr^3 ++ 3e−→Cr −0.74
Zn^2 ++ 2e−→Zn −0.76
2H 2 O + 2e−→H 2 + 2OH− −0.83
Mn^2 ++ 2e−→Mn −1.18
Al^3 ++ 3e−→Al −1.66
Be^2 ++ 2e−→Be −1.70
Mg^2 ++ 2e−→Mg −2.37
Na++ e−→Na −2.71
Ca^2 ++ 2e−→Ca −2.87
Sr^2 ++ 2e−→Sr −2.89
Ba^2 ++ 2e−→Ba −2.90
Rb++ e−→Rb −2.92
K++ e−→K −2.92
Cs++ e−→Cs −2.92
Li++ e−→Li −3.05Calculating Standard Cell Potentials
In order to function, any electrochemical cell must consist of two half-cells. The table above (Table23.2) can
be used to determine the reactions that will occur and the standard cell potential for any combination of two half-
cells without actually constructing the cell. The half-cell with the higher reduction potential, according to the
table, will undergo reduction, while the half-cell with the lower reduction potential will undergo oxidation. If those
specifications are followed, the overall cell potential will be a positive value. The cell potential must be positive in
order for the redox reaction in the cell to be spontaneous. If a negative cell potential were calculated, the reaction
would not be spontaneous. However, that reaction would be spontaneous in the reverse direction.
Sample Problem 23.1: Calculating Standard Cell Potentials
Calculate the standard cell potential of a voltaic cell that uses the Ag|Ag+and Sn|Sn^2 +half-cell reactions. Write the
balanced equation for the overall cell reaction that occurs. Identify the anode and the cathode.
Step 1: List the known values and plan the problem.