For the voltaic cell \(Co|Co^{2+} || Ni^{2+}| Ni\); the half-cell reactions are

\(Co \rightarrow Co^{2+} + 2e^−\)

\(Ni^{2+} + 2e^− \rightarrow Ni\)

The half-cell reactions for the voltaic cell Co|Co2+ || Ni2+| Ni are:

Anode:

\(Co \rightarrow Co^{2+} + 2e^−\)

Cathode:

\(Ni^{2+} + 2e^− \rightarrow Ni\)

The anode is where oxidation occurs, and the cathode is where reduction occurs. In this reaction, cobalt is oxidized to Co2+ at the anode, and Ni2+ is reduced to Ni at the cathode.

The oxidation half-cell reaction shows the metal that is oxidized, the ions that are produced, and the number of electrons that are transferred. The reduction half-cell reaction shows the metal that is reduced, the ions that are consumed, and the number of electrons that are transferred.

The correct order of the metals in the half-cell reactions is also important. The metal that is oxidized is always written on the left side of the half-cell reaction, and the metal that is reduced is always written on the right side.