mercury-mercury(2) half cell and chlorine-nickel half cell
The half-cell reaction for a mercury-mercury(II) half-cell is:
Hg(l) → Hg2+(aq) + 2e-
This reaction involves the reduction of mercury(II) ions into elemental mercury at the surface of a mercury electrode.
The half-cell reaction for a chlorine-nickel half-cell is:
2Cl-(aq) → Cl2(g) + 2e-
This reaction involves the oxidation of chloride ions into chlorine gas at the surface of a nickel electrode.