Which cell will measure standard electrode potential of copper electrode?
When an electrode potential (which is a potential difference that develops between the electrode and electrolyte), has values of the concentrations of all the species involved in a half-cell equal to unity, it is known as standard electrode potential.
The standard hydrogen electrode which is assigned a zero potential for all temperatures to measure the potential of the given half-cell. The electrode is represented as Pt(s)|H2(g)|H+(aq) and the equation is given as H+(aq) + e-→ 1/2H2(g).
This leads to the conclusion that the pressure of hydrogen gas is 1 bar and the concentration of hydrogen ions in solution is 1 M. We place the SHE on the left and copper electrode on the right, which will help us find the standard reduction potential of copper electrode.
If the concentration of copper’s reduced and oxidized forms are at unity, then the reduction potential is equal to standard potential. So, for the half-cell equation,
Cu2+ (aq, 1M) + 2e–→ Cu(s), the cell that will measure the electrode potential is
Pt(s)| H2 (g, 1 bar) | H+ (aq., 1 M) || Cu2+ (aq., 1 M) | Cu.
Thus, the correct option is (iii).