Q.Calculate the standard emf of the cell $\text{Cd} \mid \text{Cd}^{2+} \ \| \ \text{Cu}^{2+} \mid \text{Cu}$ and determine the cell reaction. The standard reduction potentials of $\text{Cu}^{2+}/\text{Cu}$ and $\text{Cd}^{2+}/\text{Cd}$ are 0.34 V and -0.40 V respectively. Predict the feasibility of the cell reaction.

A galvanic (voltaic) cell converts a spontaneous chemical reaction into a usable electric current, and it does so by physically separating the oxidation and reduction half-reactions into two half-cells joined by an external wire and a salt bridge. The Daniel cell is the archetype: a zinc strip in ZnSO4 solution (oxidation half-cell, $\text{Zn} \rightarrow \text{Zn}^{2+} + 2e^-$) is joined to a copper strip in CuSO4 solution (reduction half-cell, $\text{Cu}^{2+} + 2e^- \rightarrow \text{Cu}$) via an external wire and a salt bridge of agar-agar gel with an inert electrolyte such as KCl.

Electrons flow from the zinc anode (negative, as it steadily loses electrons) through the external wire to the copper cathode (positive, as it steadily consumes electrons), while the salt bridge maintains electrical neutrality in both compartments — Cl⁻ migrating into the anodic side to balance rising Zn²⁺, and K⁺ migrating into the cathodic side to balance falling Cu²⁺ — without ever letting the two solutions mix. The cell keeps running only until the zinc electrode is fully dissolved or the Cu²⁺ supply is fully reduced; where reactants or products cannot themselves serve as an electrode, an inert electrode such as graphite or platinum is used instead. …