# Standard Potential

The overall energy of the outer electrons for a material depends on the temperature of the systems and also, for a material that is not a pure solid, also depends on the concentration of the reacting species. Thus, in measuring the electrochemical potentials, both the temperature and the concentration must be specified. The standard potential, given the symbol E0, is the electrochemical potential at 25 °C, with gasses having a pressure of 1 atm and solutions a concentration of 1 Molar (1 M or 1 mol/liter).

## Hydrogen Reduction

$2{H}^{+}\left(aq\right)+2{e}^{-}\to {H}_{2}\left(g\right)$

The standard potential of the reduction /oxidation reaction pair is the sum of the standard potentials for the half reactions (to avoid continually having to say the oxidation and reduction reaction, they are more generally termed a half reactions, since they make up half of the overall redox reaction). The values of common half reactions are listed in Tables of Standard Potentials.

## Copper Reduction with Standard Potential

The zinc undergoes an oxidation reaction, so the direction of the reaction and the sign of the standard potential must be reversed to give the oxidation/reduction reaction pair is: