The cell emf depends on:

Temperature

The correct answer is Option (3) → Temperature

Core Concept

Cell emf depends on the nature of electrodes, concentration of ions, and temperature. It does not depend on size of electrodes or volume of solution.

Explanation of Each Option

(A) Size of anode does not affect the emf of the cell because emf is an intensive property. Changing the size of the electrode only affects the rate at which the reaction can occur, not the potential difference generated between the electrodes.

(B) Size of cathode similarly does not influence emf. Increasing or decreasing electrode area may change current capacity but does not change the inherent tendency of the redox reaction to occur.

(C) Temperature directly affects emf as seen in the Nernst equation. The term involving temperature (RT/nF) shows that emf varies with temperature because reaction equilibrium and ion mobility change with temperature.

(D) Volume of electrolytic solution does not affect emf as long as concentration remains the same. emf depends on ion concentration, not the total amount of solution present.