Reference no: EM13125108

Standard potentials measured against the standard hydrogen electrode

Standard potentials are measured against the standard hydrogen electrode (S.H.E.). Because it is not always convenient to use a S.H.E., often other reference electrodes are used. The saturated calomel electrode (S.C.E.) is one commonly used reference electrode, with a potential of 0.242 V versus the S.H.E. Using a table of standard reductions, determine what the potential of each reduction below would be versus the S.C.E.

a) Ag+ (aq) + e- Ag(s) _____________V
b) Ni2+ (aq) + 2e- Ni(s) _____________ V

When the S.H.E. is paired with the reduction of Al3 to Al, the total cell potential is E = -1.677 V. We arbitrarily assign the S.H.E. a half-cell potential of 0.00 V, so the aluminum half-reaction is assigned a potential of -1.677 V in reference to S.H.E. When S.H.E. is paired with S.C.E., the total cell potential is E = 0.242 V. If S.C.E. is chosen as the reference point (such that its half-cell potential is 0.00 V), that means that S.H.E. has a reduction half-cell potential of 0.242 V.