Which of the following is NOT listed as a factor affecting electrode potentials?

• A. Electrode composition
• B. Electrolyte composition
• C. Ambient light
• D. Temperature

Answer: (C)

Electrode potentials are governed by the redox couple and the environment that affects ion activities and the electrode material. The material of the electrode sets the intrinsic tendency to gain or lose electrons, so different metals have different standard potentials. The composition of the electrolyte matters because the activities of the reacting ions (and the presence of a supporting electrolyte) shift the reaction quotient, which changes the measured potential through the Nernst equation. Temperature also plays a role: as temperature changes, the factors in the Nernst equation and ion mobilities adjust the potential, so E can move with temperature.

Ambient light, on the other hand, does not typically affect electrode potentials in standard electrochemical cells unless you’re dealing with a photoelectrochemical setup or a light-sensitive electrode. In ordinary conditions, light does not alter the equilibrium potential.