Question

The emf of a cell should be positive for a spontaneous reaction. Give a reason.

Answer 1

[The emf of a cell must be positive for a reaction to occur spontaneously. This is because the Gibbs free energy change (ΔG) and the cell potential (E) are related by the equation:

ΔG = −nFE

Where n is the number of electrons transferred, and F is the Faraday constant. For a reaction to be spontaneous, the value of ΔG must be negative, which requires the emf of the cell to be positive. A positive emf, therefore, indicates a negative ΔG, satisfying the thermodynamic condition for spontaneity. In simple terms, a positive emf shows that the reaction releases energy and can proceed without any external energy input, allowing the redox reaction in the cell to drive an electric current through the circuit.